Is it worth it to use the 400 or should I keep my 350 in there. The TH350 is already installed and has a shift kit. I have a TH400 I pulled out of an olds. What are the differences between the 350 and 400. Or should I just keep the 400 as a spare for down the road?

 

I'd build the 400 myself. I only put a th350 in mine since it's what i had. When I step the power up it's getting a th400.

 

You also need to check the bellhousing on the oldsmobile TH400. There is a difference between the Chevy Th400 Bell and the rest(Buick, Cadillac, Olds, Pontiac) There may not be an issue but I know there are differences....

 

Ive went through three th350s. If your making a decent amount of power, the th400 hands down.