.........and now you don't.
Don't try this at home with a stock chassis. I only did this Hannibal Lecter surgery because of the frame connectors (Wish I knew of Chrome Moly frame connectors back then) and 12 point roll bar that together strengthen and stiffen the chassis more than stock.
On a stock unmolested chassis, these rocker panel bridges are very integral to the chassis strength. This only saved 1 Lb between both sides.

Here's something that I've forgotten about and maybe it was because it was FORD related but maybe could work on Mopars via similar bolt patterns.
At the street haunts back in the early 90's, I took note to some fast Street Mustangs running what appeared to be Donut spare wheels as front runner wheel/tire combo's. I shortly found out that they were indeed using the Donut spare wheels out of Lincoln Town cars and or Marauders and installing skinny front runner tires on them. In some cases, even using the 50 MPH limit spare tires themselves.
Why you ask?
Idiots, but not so idiotic in terms of necessity.
Here's why.
Some or all of those Donut rims were actually lightweight forged Aluminum wheels and after being painted black, they could surely fool their own kind. Not this cat though, I've busted a share amount of cheats on the streets and these were some savvy cats out on Fountain Ave and 150th St.
Anyway, I never talked about it for reasons that nodded towards safety. I was not at all Kosher with spare wheels being pushed past the 130 MPH limits.
It would not surprise me if on occasion,this thread leaned towards the stupid things that were done to cut weight. I've got many stories behind that curtain.LOL.

With subframe connectors in place, what you are creating is a boxed area in the area. The connectors act sort of like an annexed bridge to the factory rocker panel bridge.
As in this crude quick drawing I made below, you can see how the longitude rectangular tube that goes from front to back is also tied in with the transmission crossover tube and a similar sized tube out back just past the rear door jam. This combined with the longitude tube welded to the floor pan also brings more strength to the area.
What I've done is the furthest I would go since it is only oval shaped holes dotted carefully down the bridges topside, so I would not worry about it if you've done the same.

Not concerned at all at this point but these are good thing to keep in mind while lightning these things.

Go lightweight the right way.

Really enjoying this thread, I thought I was anal about weight loss but you are taking it to a whole other level! So, where can I buy a set of those titanium UCA cams? I'm after some titanium K frame bolts as well...

Dartbloke.
The gentleman based in Detroit was not really thinking in making any others as they were a home project on his own car and the pieces are hard to machine and relatively expensive. That being said, maybe he might get to making a few more batches if a few come together to order them, then it might be cost effective for him. It's ultimately up to him and the customers.
I think he's aware of the interest and might chimmey in here some time soon. Though he manufactured his own K-member bolts as well, and they were beautiful, I had already machined my K-member bolts over at Trick Titanium in Troy Michigan quite a few years back.

If I may and maybe you have done so already, you may want to first focus on the heavier and larger objects in your car that could shed some weight giving greater results.
I have a few major and relatively large tricks still to be applied to the car, but I am now focused as you probably know on the more anal and sometimes expensive minute parts and fasteners that only equate to ounces in most cases.
I must say though, it's the most fun part of it all. At the end of the day it's all about numbers so I affectionately call it the art of "Arithme-tricks". You heard it here first.

Well if there's ever any kind of group buy on this kind of thing I'm in! I'm in the early stages of my Valiant build and sure there's big chunks of weight yet to come out. Whatever part I'm working on gets the full treatment before it goes back on, front suspension is next so whatever lightweight parts I can lay my hands on will get fitted next.

I sure would be in on that group pot as well just to have an extra set sitting around for conversation.
Remember that Tubular upper control arms are a little lighter than stock arms, at least the Magnums are.

Aluminum strut bars and their aluminum washers are lighter than stock.

Bobs fabrication of chrome moly center links are lighter than stock.

While you're at it, his chrome moly steering shafts are lighter than stock.

Titanium lower shocks mount bolts and the upper nut are lighter than stock.

Stock non sway bar lower control arms are lighter than their sway bar counter breeds.

Titanium screw on or knurl type wheel studs are lighter than stock.

Titanium tapered seat or aluminum shouldered lug nuts are lighter than stock.

Stock drums are lighter than stock Disc but leave a lot to get used to. You have to have good USA parts and savvy driving skills in traffic as well as past the stripes at the track.

Of course, Centerlines smoothie stealth type 3-1/2 front wheels (Shown below) are lighter than stock and almost, just almost look like a steel wheel. I'll post better flicks later.

Yep, already got the ally strut rods, tubular upper and lower arms, lightest Strange discs and all titanium bolts. Still searching for titanium wheel bolts and aluminium nuts. Will have to speak to Bob about a moly centre link, will be making my own tubular column.

Reaching back into the deep bowels of this thread, here's my aluminum stock looking column if you haven't seen it already. Had it made as a one of one since it was a case of twisting elbows to get it turned on a lathe by a very busy machine shop.

Aluminum Tie rod sleeves is another plus to minus the pounds.

You can get shouldered 1/2 X 20 titanium lug nuts at a company called Met-Tec here in the states.
Ti64 is another firm that has the acorn type tapered seat lug nuts in titanium.
I also know of aluminum tapered front lugs from a company called Mcmasters in Chicago. They are nation wide for distribution though.

Not so better flick of the front wheels. Closer one later.

Close up of the elusive front wheels.
These were the closest that I've known so far to look like a stock steelie and I got the very first pair off Centerlines first initial run of them.
I only wish a reputable wheel company could spin a batch for us Moparites.

In other lightweight news, AMD spent a good amount of loot on dies and stamps to create aluminum body panels for the Camaros and Novas and nobody came to the party, except maybe a rogue F.A.S.T guy here and or there.
They wrote to me saying that they will not be making anymore light alloy panels for ANY car. Sounds like someone is mad at the bean counter.
Now if they would had made some lightweight panels for the cars that came with them in the first place, (ie: 63'-64' and throw in a 65' for good measure, LoL) then maybe, maybe they would have made more sales. At least more than the GM's.

Here are some acorn type lugs.
Combined with Ti studs and some unneeded rotational weight can be shaved. Wish it was rotational weight taken off on the outer most part of the wheels where it counts the most.

Having some stuff welded by an excellent old school welder cat. Will keep you'll posted on stuff coming down the belt.

Who's selling the alloy Dana? struggling to find any mention of it online...

Baxtek fabrication in Palm coast, Florida. They have a website Baxtekmoto.com and show just one picture of the Dana, but not really anymore than that. It is part of a 67' Dart project street car that they are building and also had at the Nats.
I've reached out to them, but no response as of yet concerning further questions. Maybe they are busy being that they service the motorcycle industry.
Since this is a new product, maybe they (Baxtek) should show us real world performance strength and weight on a scale.
It was a very nice looking piece, but you know as they say, Don't judge a book by........

A tiny bit of progress on the horn ring sculpting as of late. This is the unit welded together sans the CORONET face bar sitting on top. It now weighs in at 1/4 pound.
Will have the whole unit finished and welded some time next month or before.
Busy with other things at the moment.

At least once a year a factory pro stock dana w/a magnesium center section shows up on ebay.