th350 to th400 swap questions

[MylilBowTie]

I have some questions about a transmission swap. I currently have a TH350 (9inch tailshaft) that has been rebuilt no less that 8 times in six months time including rebuild time about one work week each time. So I bought a TH400 with bolt on yoke inch tailshaft. I found out that it came out of a 1984 G20 van. Supposed to have been rebuilt and good to go. I have started to think what all has to be done to get this switched over to the TH400. I have a one piece driveshaft now that is stock length for TH350 nine inch tailshaft with an 8ft bed. What I'm wondering is can I use a one piece driveshaft with a slip yoke 33 spine (TH400) and not have any problems or issues with it? I know its a little short if I use it but I would have it lengthened. I know a little bit about two piece driveshafts but never messed with a two piece driveshaft. If I have to use a two piece all I need to do is buy it and drill tap two bolts for the carrier and be done with it. I might already have the bolt holes there but I don't think I do. Cross member has to be moved back I know that.

TH350 is 30 11/16 long - TH400 is 28 3/8 long. Using a one piece, if I done it right I would need a 2 5/16 longer driveshaft right? I rather use a one piece but if its cheaper to buy the two piece I will use that. Pricing slip yoke for TH400 is 75.00 -130.00. Plus I will have to have driveshaft lengthened and balanced. I have yet to call how much that will run me. Plus that would be a good time to get the bigger TH400 ujoints installed.

The other thing I was thinking about is the u-joints the TH400 are bigger than the TH350. I know I can get a u-joints that have TH400 one side and TH350 other. But I would like to have front and back the same size. Would the TH400 u-joints fit in the rear yoke? Im lost as to what the different sizes and all that are.

Has anybody run the Lokar Kickdown kit for the TH400? Looks to be a lot better setup than the B&M switch.