I am at the point now of replacing the floors so I thought it would be a good time to decide what transmission I will be placing in. I really like the fact of having a 0.50 gear ratio that way I can place a dana 60 4.10 in the rear and cruse at low rpms on the highway. I was wondering what you guys think and if you would prefer the 5 speed or the 6 speed. The floors all need to be replaced and trans tunnel so that is no biggy.

I think the 5 speed will be a significantly easier swap. The T-56 is going to require you to cut and make a custom trans cross member. It is significantly larger transmission.

All that said - I'd go with a T-56... but i'm biased

Yeah I can tell haha but are you glad that you went with the 6 speed. I have to replace the tunnel anyways so either way I have to put the tunnel back together again. How did you go about finding where you wanted the trans to set and angle it sat at?

I went with a T56 in my car too (non-Mopar though )

If you have to remake stuff anyways, I don't see why not have the advantage of the extra gear

And I just set the engine and trans angle the same it was as the donor car basically...

I had this same debate over a year ago ultimately i went 5 speed with a.64 overdrive. I have 3.91s out back and im running a 28 inch tire putting me at 2100 at highway speed (70mph) with a t56 thats 1600 with 4.10s the 5 speed would put me at 2200 with a t56 speed thats just over 1700. My car runs ok at 1700 but my cam doesnt really start in its curve til around 2200 or so, that being said dropping to an even lower rpm then i am currently would result in a bog feeling on the highway. The t56 is nice i wont deny that however with all the extra fabrication and modifications to suspension components (torsion bars and crossmember) it takes to put one in a classic mopar and as above mentioned depending on cam specs etc i found it to be an easy choice for the 5 speed in my vehicle.

I've been thinking about a t56 too. Just wondering how much power a t56 out of a mid 2000's GM will take. I know if you cough up the cash there's a gun on ebay selling t56 magnum's for around 3k, supposed to be good to 700ft-lbs or something like that. Another option would be a tr6060 out of a challenger or newer camaro.

I probably wouldn't want to run a .50 overdrive gear without port fuel injection. A carb might not be making enough vacuum at that load/low rpm for efficient fueling.

with EFI, I say go for it. but with a carb, I'd say try to keep your cruise RPM above 2000 rpm, or run a "stock" cam with no lope, that is all done power wise, by 5000.

my big block was running a cam that was 1800-6000 rpm power band. I had a TKO with the .64 OD and 3.23 gears with 28" tires.

5th gear was useless unless I was going 70mph or faster, at 65 my RPMs were down at 1700-1800, and the engine was lugging and surging. I tolerated it for a year or so because I knew the whole time that I was planning on 4.56 gears in the rear. and once I did, everything was great! tons of low end, and yet I could still cruise the highway at 2400 rpm, smooth as glass at 70mph.

the TKO will be smaller, and with the .64 OD you don't really need 6 gears. in a 1/4 mile run, you probably will NOT be shifting beyond 4th gear. I feel like you really only need 4 gears for pulling, then a 5th gear OD for cruising.

with that TKO I was running, the 4.56s, 28" tires, the top of 4th gear for me was up around 110-115 mph. I don't need more gears beyond that!

I went with the T-56 for my 56 Dodge 408 Stroker. I will run it with the EZ-EFI setup.
I did a lot of research and unless you can rebuild and upgrade a GM T-56 the brand new in the box Magnum T-56 for about $2800 or so is the way to go. (a GM core will be 800-1200, and you are looking at nnother 800+ for a good rebuild and upgrade).
Yes they are BIG but the effort will be worth it.
I also have a fairly comprehensive parts list with prices for what it will take to install one to a small block. I learned that I could buy a complete kit for only a few hundred more than I could cobble it together myself.

That gave me some new insight on my pro cons for a 5 vs 6 speed. I would like to have a nice lobing cam. I will more then likely have a 4.10 rear end running 26 inch diameter tires. I know I won't get great gas mileage but I do like not winding the engine out when I am cruising down the highway. What kind of mileage do you guys get out of your 5 or 6 speeds? I know there is another forum but that is for stock 440's without overdrive.

Another vote for the T56 , worth the effort

Yeah...I'm leaning toward the 6-speed it has a really nice wow factor. If I ever wanted to go with a higher rear end it would be easier to deal with on the street. The thing is do they make driveshafts to use for this conversion or is it a custom kind of deal? I also heard the location of the shifter is too far off of the stock mounting hole that it can't work with the stock center console.

Shifter will be different by a bit unless you use something like a keisler tko 5sp where they relocate the shifter to the correct position. I already decided a long time ago I didn't want a center console anymore so I sold mine to get just the bare shifter on the floor with bucket seats look.

Another issue is I've heard the tremec 5sp's don't shift so well over 6000rpm but I haven't heard this about the t56's.

With a 5 speed you need to choose what to do with 5'th gear. Is it a performance gear - ie. best top speed - or is it set up for cruising. The best cruising setup will usually be too tall for max top speed. With a 6 speed, you can have both. Since its already "under the knife" I'd the 6 speed.

I used a LS version of the T56 magnum, It puts the shifter a little further back. I rasied the tunnel 3 inches and wide 4 inches.

what are you guys doing for carpet when you modify the floors this much. i really can't see how the stock carpet is supposed to fit.

Any good interior guy here could make anything. Mine will have to be custom made. I plan on making a custom console plus my roll bar mounts.

Yeah I don't plan on using the center console really either. Where are you guys getting your drive shafts from? or are you having them custom made? I feel like I would regret not going with the 6 speed and I wouldn't miss the 5 speed lol. At first I will still use the torsion bar suspension. now can I get the 6 speed to mount without moving there locations at all and compromising structural integrity.

The driveshaft will have to be custom made. Mine came as part of the kit that included the bell, clutch, flywheel, hyd bearing, bolts, etc.

I believe the yoke is a std GM size.

As far as the floor, you can make a LOT of room with an acetylene torch and an 8 lb hammer. I cleared about 2" at the bellhousing just by heating and stretching the metal.