TH350 to TH400 swap

[demian5]

Before you say "Put a 700R4 in it" please read the post...

My truck is a 1970 long bed with a small block and column shift. 307 rear diff with 31" rear tires. Currently building a 385HP motor.

I have a TH350 in my truck and I need to rebuild it since the motor will wipe it within minutes (its already slow to engage when cold).

I also have a complete TH400 sitting in my garage that I could get rebuilt as well. This would be a strong trans for my driver.

I rarely tow or haul with the truck, and the 350 would work fine rebuilt properly and upgraded where needed. The gearing requires me to put a stock stall converter in it, and I chose my camshaft for this combination (268H Comp Cam). Also, the 400 takes more power to operate than the 350.

If I decide to put the 400 in it, what do I need to buy and/or change on the truck itself to bolt the trans in?

1. Trans Kick down switch
2. Cross member - move back or need new?
3. Shorten driveshaft?
4. Shift linkage?
5. ?
6. ?

Thanks in advance - I want to do the right thing the first time.