From about 86/87 on gm took the 4 center bolts on the manifold and tilted them up for better access. I would buy the heads as well, You will have to elonggate the hole to mach the heads and then you may not get a very good seal and the possability of oil leaking from the bolts. If you dont want to buy the heads you can look for a older TPI setup that will fit the older heads. Are you getting the computer, wiring harness and all the sensors as well.