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Discussion Starter · #1 ·
Boths cars are '71

Car A: 307cid, TH350
Car B: 402BB, TH400

I want to put the big block into car A, but keep the TH350 trans. Will either of the two driveshafts just work and not requires changes? I'd like to not hack up the driveshaft in Car A, as I'm sure a small block will go back into it before too long.
 

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Original shaft in car A will work still with a BB & TH350.
Engine sizes doesn't matter...the trannys are different lengths.
When swapping in a TH400 in my wagon from a TH350, the driveshaft needed to be shortened approx 1.5"

BTW...car "A" is a '72 :D
 

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Many years ago I had a 71 Nova with 307 and TH350. I installed a 454, kept the TH350, and Bill is exactly right...no need to swap or modify driveshaft. The only "gotcha" I can think of for this swap is that your 307/TH350 probably has the small flexplate and your 402/TH400 probably has the large one. You'll probably want to keep the large flexplate so as not to require purchase of a new starter. I think you can use the TH400 torque converter with a TH350, so you can just use the 402 flexplate/starter/converter for your swap.
 

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A BB, and a SB, are physically the same lenght from the motor mounts back.

It's the Trans You chose to use that will dictate what Driveline You need to use.

Just keep the same driveline, with the same Trans, and You're fine.
 

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Discussion Starter · #5 ·
Good to hear. I was thinking it would just work, but I didn't know if the "same length back" of the motors meant I needed BB motor mounts for that to be true.

Actually, they are both 72s, but who's counting? :D
 
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