I am in the process of building a 3400 motor for my olds alero. I'm not trying to build anything crazy, just a quick everyday driver. I have a 89 tgp that needs more work than I'm willing to put into it. I know the t25 is a little small for the 3400 but I already have all of the parts and can do it for practically no money. That being said I know about all the differences between the 2 motors. I know as far as exhaust manifolds I don't have a whole lot of options. I've heard that porting the 3.1 manifolds to D shape to fit there's not much metal left for sealing. My plan was to use a log style 3100 rear manifold and cutting the 2 bolt flanges off the TGP crossover and putting the 3 bolt flanges on it. If I do that will the crossover match up or is my only option porting or custom headers? Thanks