I sit corrected. I must have confused your car with another on this board.
3600 is a bit heavy.
I would suspect that at this time with possibly a limited budget, that you are in the right direction by working on shaving weight from the very front starting with the brackets.
Isn't your car a 64' Polara?

So after reading all 20 pages of this thread, I immediately got out the hole saw to start lightening my helmet, and then remembered to take it off first.

Hope I remember all this stuff correctly.

It took nearly 15 pages of replies until it was finally discussed the "stainless K's" were lighter mainly because of thinner material, which is really a poor choice of material for a repeatedly loaded suspension structural member as it work hardens with stress and soon cracks.

After finally stumbling into alum hood pins instead of steel, nobody? has mentioned rifle drilling them?

Alum for exhaust use, is not very dependent on the alum alloy chosen at the temps expected, its all close to the fail temp. And few seem to consider at even a lowly 200F, alum is starting to lose a lot strength, all factory temper will lost in first heat cycle, which just might anneal/soften alum enough that it might reduce any potential cracking, and wonder what corrosive exhaust effect may play a higher temps, with added question of race fuel additives. I was always led to believe keeping exhaust temps high (flow) was the goal, which alum does not do, and stainless does very well , alum needs to be thicker vs Stainless, which is another heat loss downside, and I wonder does this offset any performance gain in having less weight. I also wonder is a high temp ceramic exhaust coating possible and/or beneficial here?

I believe the first crossmember welder was spot on. A big /high HP car with TB's loading the crossmember, made out of welded alum, when steel has been proven to fail, with ground? welds, is a potential failure waiting to happen, IMO. The added fillet gussets are a nice improvement.

TI wheels studs if used on the street are hopefully known to have finite fatigue life, very unequal to steel.

Are composite leaf springs ever used on drag cars, because they are much lighter.

Never saw any mention of ring gear lightening.

I cringe when I see seat mounts lightened, big holes in flimsy alum? Really?

5/8" Dia Ti Bolts in front Leaf hangers.

Anybody make Ti Rear axle U bolts/tall nuts?

I think anybody going to these lengths would use a CF DS. Concern over rock induced nicks, if a real problem, would be likely only for the street crowd.

For the drag crowd, it is possible to have hollow TB'S factory sized in the lighter rates.

A current car I'm working on, since it will see street use, I'm only using one wheel of internal disc/hat parking brake.

I replaced my Holley pro strip ignition yesterday.I'd bet between the 2 boxes and the harnesses they weighed 10 lbs.
Also removed the 4 auto meter gauges that were mounted on the cowl for the last 15 years.
Can't wait to weigh and see how much I lost.Pulled on to the scales at E/town last week,,,,,,,,3850 with a 1/2 tank of fuel.
I installed a 6al,wonder what that weighs

Glad that you bring up these questions and or concerns.
From the sheer size of this thread it shows that we all have been having a lot of fun and it all looks good a dandy, but safety comes first and foremost.
As you'll know, I came on here as a guest and for the reason of Mopar family, I felt it to let out all my suggestions, tricks and mistakes in full transparency. But, let me assure you that I value all the input from everyone and I also value my safety and the safety of others because as we all know in drag racing, everything is about hurry up and wait to only go faster. but Murphy's Law happens much faster and I would only want to make and play things safe.

To answer in the order of presume.
*The light weight K members made out of thin gauge stainless PROBABLY failed because of the extreme stress from lifting and then crashing down forces incurred during a wheel stand.

After their debut to dominate the fields with their altered wheelbase weight advantages and with victory wins almost from the start, all those AFX cars of yore were known to carry the wheels a good distance while being a wild ride all the way down the track. It was a audience sensation and shortly after were encouraged by some outlaw tracks to do such wheel stands for entertainment purposes until it became inherently dangerous. As a result, a memo was sent out by the factory to all the factory drivers to stop all wheel stands immediately.

In fact some teams were warned that their respective contracts would be revoked if they continued the violent wheel stands in fear of crashes and product looks. Someone forgot to give such memo to Dick Landy. LOL.

In contrary, today NHRA presumably wants their future Pro-stock cars to have items removed or installed that enable them to perform some type of limited wheel stands at launch. Who knows how that rule will limit itself in the heat of competition.

*I've got rifle drilled aluminum hood pins on all four corners, but with an adjusting tube center for strength and adjustability.

*An Aluminum exhaust is only holding up its own weight which in this case is almost nothing. It is beyond the fail temp once at the collectors and rearward and Yes, it will temp loss at heat cycles but a strict multi-point inspection of the system for cracks or looseness keeps me worry free. I have a few Aluminum hangers through out the system to keep any cracked portions from falling off the car in motion.
I had thought about corrosive gasses when first entering the idea of an aluminum exhaust, but the issue of corrosive gases at different temps is a mystery to me in all honesty. Steel, stainless or iron go through the same phases. Aluminized steel tubing itself seems to have survived many years of on/off usage from what I've seen.

One thing you bring up that I was seriously thinking about was indeed heat loss. True that heat loss can effect HP, but I took a gamble at weight loss over the heat only because I used to run open pipes back when and now run an exhaust system that is relatively short dumping at the rear differential without tailpipes and believe that it has little to no effect on the flow.

Many cars out there, be it factory or custom or race run with aluminum hubs, drums and calibers where different temps of heat and cold are constantly introduced on crucial suspension parts.

No new ET numbers yet, but I can safely say that my car feels a lot more reactive now with less weight, less heat in the system than ever before. It could honestly also be Thumper's magic on my carb as well.
I'm just looking at all the suspects of change that have been performed lately. Maybe too many at the same time.

*As far as the trans cross member, the reason I've painted it gloss white is to have good looks at it during under car inspections. (A good habit)
I've only heard of a couple of failures with the factory cross members made out of steel and for the most part seem to be a result of miss-aligned transmissions/drivelines, bad vibration issues and or bad factory designs from the very start. Some cross members have extreme load bearing mounts that were ill-designed or ill-welded in the first place. Has anyone ever taken a good look at factory member welds? A good case is the factory steering box welds to the K member. I've heard of some of those breaking loose.
I reinforced my steering box welds because of concerns with a manual steering car which applies more stress on the tires and suspension more than a power steering unit in motion.
I've never broken my steel trans cross member that I had before partly because I also had the trans mounting bosses closer to the members center where it is more stronger because of my engine setback. (Long standing secret).

*Titanium in the right T type is stronger and less stressed then steel because of more shear and tensile strength.
F1 cars put Ti bolts to the test equivalent to many miles on a street car, especially a lightweight street car.
Though, honestly, those types of cars have strict maintenance programs in place. I do as well.

*No composite leafs on mine, though I know of some out there. Hee,hee.

*Lightened Dana rear on my car with a few unique tricks but not much weight shaved. (No I ended up not going for that supposed new wave all aluminum Dana 60 rear. They were a little stiff in answering my longevity strength questions.)

*Factory A-990 seat mounts have been flawless in my car for years, more than 15 years now and on many other Race cars that see more stress than my street car ever will. In fact I probably bought the first sets off Kramer Automotive back in the 90's.
I've also installed large washers on the floor mounting bolts to spread the load of my body shift weight during launches and quick stops.

*I have not reached the Leaf front hanger bolts as of yet. Though I have thought about them.

*I've looked into Titanium U bolts, but no one wants to machine/bend them for me with the correct flat spot on the top for more grip on the rear tubes. I do have a set of 8 Titanium long bolts on future order for the existing steel U-bolts though.

*Carbon Fiber is too easy and expensive for such a piece that can be easily nicked and shredded in a street environment.
Dynotech made me their very last metal matrix shaft just before deleting the material from their line up. In fact, my order hogged up the last length of matrix tubing that they had.

My handle of FULLMETALJACKET is for just that, the car is a full metal jacketed project. Made of many metals. No fibers or plastics of any kind for opaque items.

I'm not sure what TB's mean?

*I've run my rear drums without the parking brake mech for years.
Again, this is almost like the Woodward garage test mule back in 68' but with a concern for safety.
I for one do not encourage such crazy things unless they were thoroughly engineered, planned and or tested by logical persons.
I'm just showing what could be possible.

Al.
A Hamster in a roller wheel may ignite more fire energy for that Elephant then an MSD and Holley . Much lighter too. Just have to feed it here and there. LOL.

Not sure my initial reply warranted such a detailed worthy reply. Briefly:

1. The choice of stainless vs steel for the K, no matter what the use, was a poor choice. Which means if Stainless would work, a quality steel could also be used, in a thinner gauge.
2. My concern on flimsy seat supports centers on, a seat belt holds a driver against the seat, and in most cases, if the seat supports distort, the belts go slack.
3. I am not sure if part of the original calculation on your part, but a 3" alum exhaust with its greater surface area and thermal mass, vs say a 2.5" dia, may have been a big plus in the exhaust longevity equation, just sayin.
4. I might have mistakenly assumed the painted white crossmember was Alum as you originally proposed, is it steel?
5. My concern on TI, any application with reversible load cycles, or bending, which a wheel stud might ( OK its not supposed to), is a candidate for Ti fatigue, and the consequences very unfavorable, and hence my concern, because regular replacement at high cost is easily pushed aside. Steel is far superior to Ti regarding fatigue of course.
6. On Axle u bolts, is the flat spot that crucial? I'm sure I've seen u bolts without a flat spot. I have also seen housings dimpled. If manufacturing is that difficult, how about a 9/16" U bolts, and just machining off a 1/16"? from the inner curve, creating the flat spot, and still be stronger then a 1/2" u bolt?
7. "TB's" are my handling slang for torsion bars, sorry.

Here's another worthy response since I'm such a detailed guy. LOL

*As far as stainless in thinner gauge for such a crucial part member, Yes, I would be a little high nerved on a high strung wheel standing car, especially a heavy car. But on a decent HP car that sees hardly a wheel stand on launches like mine, then yes I would try it while keeping a close eye on its stress points.
In building one, 440 Stainless would be my choice where as 304 stainless is my second. Back then, it was different stainless quality metals that they tried. Even a few or so Magnesium samples were made. Crazy.

I don't rag and trash my car while driving under normal conditions, I see to it to save it for the runs.

Why?

A friend of mine here in Brooklyn way long ago had one of the 65' stainless units on his heavy 3750 LB Plymouth Hemi street race car and didn't have any problems till he started with the wheel stands. Shortly, it showed signs of cracking. He threw in the garbage years later and way before I got to hang with him enough to talk about it.

A thin gauge steel member might not survive as well. Stainless to my knowledge gets its strength from not only the temping, but also the chromium that is part of its properties.
I'm honestly not at all a well tuned metallurgist here.

*As far as what I have seen, experienced, tested and so on.......
Those aluminum seat brackets have gussets introduced to the inner sides. Like mentioned before they have served on my car for a long time with no cracking issues what soever from regular service. They are strong but not as strong if they were steel and if it were so, it would defeat the purpose.
Then again, plastic racing seats are only as strong as their impregnated steel gussets and bolt bosses. The plastic could shred and or crack wide open in a bad crash, so I think it is irrelevant.

*Yes, part of my original calculation of using a 3" exhaust has to do with heat expansion. Probably would keep more heat in the system along with torque in the curve if it were 2.5 ID, but I wanted to make sure I did not have aluminum soup on the street.

* The white cross member is aluminum and gusseted in every way possible using T-6 grade.

*6AL-4V T titanium which is in question here can hang in stress points as much as steel can. But probably not as strong as high tensile steel bolts. It also has high anti-corrosion properties unlike steel.
Used in many high stress military, marine and aircraft/aerospace industry internal engines and turbines where there is a lot of stress and heat.
Also consider that there are (5) 6AL-4V T studs holding each wheel onto the hub. 7075-T Aluminum hubs by the way.

*Now thinking about it, Lightweight Axle U-bolts can take a vacation as far as I'm concerned only because a good hooking car puts a lot of stress on those bolts as the rear tries to twist itself around on the hit. The leafs, driveshaft, gears climbing on each other along with the weight of the car are all calling on those bolts.

*I would never play with hollowing out TB's (Torsion Bars)since they hold most of the front weight up in the air and take lots of load under bouncing (Street use) or landing (wheel stands).

FWIW, current issue of "RaceTech" magazine has a multi page article that states in F1, the current cost per single pound of weight reduction, is in the the range of $25,450 to $50,900 per pound.

Might have been my '63 330 you were recalling.

It weighs (weighed) 3,287 lbs. this spring.

I suspect the new forged crank and rollbar going in will add a few lbs. this fall..

Not surprised since I have walked away from some quotes from F1 suppliers. Most of them being in the UK and Italy.

In retrospect, my budget has been modest to say the least since I spend dollars lightening the load that I make reselling my good used parts that I want to upgrade or are simply a little or too heavy.
I'm looking at long term service where a relatively mild motor pulls a low weight car down the track in the neighborhood of some high strung combos.
It's a question of how long someone intends on staying in this game.
If it's short term and quick rally to the winners circle followed by dullness, then high strung high dollar combos are the answer with great results. If you are in a keepers game and love inventing as you go along and don't/can't have time or $$ to make power, lightweight is the way to go. Though lightweight can be expensive as well if not planned right. As you can see, a lot has been hand built here with little to no cost.

I've studied F1, NASCAR and Dirt/Circle tricks to come up with some crazy combos based on how they are/were applied in those sanctions. They were sick in Stock car/NASCAR back in the late 50's and 60's. The hey day of invention without big corporation intervention.

Find 1600 places to smartly remove an ounce and you'll get back in the ballgame.
I cringed when I went with a roll bar in my car for safety, but I chose Chromemoly to get some shavings back.
That's a good weight at 3287 Lbs. I better step up my game.

When I quit smoking/took up jogging and became a (~80%) vegan I lost more weight than the weight of going to aluminum with the 'source heads/intake/pump housing/master cyl/radiator/rims all combined (felt better too) & the car was much faster/handled better. gradually is the key (ex for the smoking)

Good doing.
The only smokin' you should be doing is smokin' the competition.
Remember to wear no underwear, one aluminum ignition key and fast the night before to really bring the weight down. LOL.

Ever heard of a Grandfather scale?
Only in Detroit.

Wow haven't seen one of those in a few years, like maybe 32 years. I spent 8 years in the scale business from 76-84 and learned and worked on mechanical dial scales just like that. Very intricate inside. I had to make them liner all though out the dial, it was a challenge to say the least, I always had weights and measures inspectors checking my work, watching me work.

Then load cells were coming into play and forever changed the way we weigh things.

I haven't read the whole thread, but it sounds like are are obsessed with weigh savings, I salute you, cool deal!! and super trick.

Thank you. Just sharing some ideas and possibilities. The secrets were eating me inside out. LOL. The Law of the street I guess.

Yeah, that scale was butter and I just stood there staring at its beauty along with the countries pride from back when.
Company that still uses it has been in business for 70 plus years and supplied both Ford and Chrysler with all breeds of metals. I was in a candy store.
I have a small old school 1960's scale in my studio and a digital ounce and gram scale for the minute stuff.

Ya'll should see my welders shop here on Long Island. Over 60 years in making stuff for the aerospace and military and yours truly. Expert precision welder with great manners and very reasonable. Here are some peeks.

I think you might need to tell me where this place is...

Great replies to some tough questions BTW. You have really thought this stuff out.

All in good standing. If I were just bumping into this thread, I'd be curious and or suspect of such things and if they have been thoroughly thought out as well. I'm still testing, its a mule thing but within reason.
There might be some items that reverse back to total stock, but so far all is good.
There are places where there is a good portion of weight to be removed and I won't go there.
I've read about some rather unorthodox moves and grooves from the factory engineers themselves back in the day and for the most part, we all still apply and run those tricks, but some were out of this world and not to be tried at home.
Case in point, Aluminum headers. Wow!

Al, you want a refill on that Popcorn?
You'll pick up weight if you do.