Shift adapter is optional. Driveshaft is the same. I do recommend a new torque convertor. The kick down is different but cheap.

I don't believe you have your math correct at $500 difference. The difference is at least twice that. If you are talking just savings in gas it's going to take 20000 miles of highway driving(in overdrive) to even come close to breaking even.

I'm not an advocate of either. I see the good points of both. Since the original question asks about the 350 I'm leaning that way for this thread for obvious reasons.

QUOTE: Guys, I believe that my ST300 has some major issues and instead of trying to rebuild it, I would like to swap it out for a Powerglide or TH350.