1978 Pontiac Grand Prix Transmission

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Apr 26, 2021
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Nekoosa Wisconsin
Okay so I own a 1978 Pontiac Grand Prix and it’s a roller. Car was originally a V6 with a th200 or whatever came with the V6. I have a chevy 350 and also a th350 that I’m going to throw into the car, and I was wondering how much modification it will take to install the th350? Can I use the stock transmission’s crossmember? Do I have to buy an aftermarket crossmember? Any help would be greatly appreciated.
 

g0thiac

G-Body Guru
Sep 6, 2020
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Okay so I own a 1978 Pontiac Grand Prix and it’s a roller. Car was originally a V6 with a th200 or whatever came with the V6. I have a chevy 350 and also a th350 that I’m going to throw into the car, and I was wondering how much modification it will take to install the th350? Can I use the stock transmission’s crossmember? Do I have to buy an aftermarket crossmember? Any help would be greatly appreciated.

Direct swap for the transmission, although I believe TH350 needs some sort of vacuum compared to the TH200.

Not sure about the engine mounts for the 350, someone will have to chime in on that.
 

pontiac guy

G-Body Guru
Oct 28, 2016
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Royse City, TX
The trans is a direct bolt in. You do need vacuum for the modulator or it will shift a little funny. The motor mounts need to be swapped on the frame. They are different than the V6 stuff. Your springs are a bit soft so it will squat some. Radiator is too small for the SBC and you need the chevy fan shroud, brackets pulleys etc. Check the fuel pump location as well.
 
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