I was just wondering, I was thinking of looking for a used factory y-pipe. I want the one from the 85-90 TPI cars, that uses a single 3" cat, and is slip-fit on the y-pipe side, and ball-socket on the I-pipe side.

I was wondering though, would that y-pipe bolt up to my stock LO3 manifolds?

It would make doing exhaust so much easier, because then I wouldnt have to buy all the parts like headers, cat, all that at once. I could get a junk factory cat from the same exhaust system, and hollow it before I put it on the y-pipe. Then, I could keep a fresh 9118 type cat for emissions time. And get any full 3" catback I wanted.

 

No. The left side is close enough, but the right side is completely different. You have to swap the manifolds and y-pipe together.