I have a good source on a TPI from an 87 IROC 350. My question is will the 87 TPI base fit properly with my ZZ4 heads. Hearing conflicting info on the bolt patterns. ZZ4 is not vortec bolt pattern, right? Should I do this or not? Thx, JT

I think 87 was the first year for the different angle on the two middle bolts. The TPI would bolt up to the ZZ4 heads.
If you have not bought the engine yet, what I would do would be to buy the 385HP version with the fastburns, then get the Scoggin Dickey vortec TPI base plate. The fast burns are a much better head than the ZZ4s. SD got 425HP from a 350 FB engine, HOT cam and Accel runners.