I swapped out the 305 tpi for an 84 Vette engine with a carb, I kept the tpi's exhaust headers and I just tried to fit up the stock Y pipe, but it seems the oil pan is in the way!! Not having the tpi motor to see if the oil pans are different, has anyone else run into this problem? Looks like I'll have to add about an 1" to 1 1/2" to the legs close to the exhaust manifold to make it work,

 

Update----Oh for sure the pans are different, I found a pic.

 

The F-body cars motors were slightly different than the Vette motors. I'm glad you figured out the difference! Now you'll just need a shop to fab up an exhaust for you!