When the heads changed it 87 does the block remain the same?
I am just trying to find out why pistons and crank kits say 1968-1986 i always thought that just the heads changed. and if i rebuild a 350 block that had centerbolt heads will the old style heads bolt to the block? Any help would be very appreciated!!

 

Head mounting bolt, coolant passage, and dowel hole locations are the same.

During the 1986 model year, the case was changed in the crank area to incorporate a one-piece rear main seal, which is why many manuals and parts listings differentiate between the pre-1986 cases and later ones. From the perspective of the heads, there was no difference until the Gen II engines were introduced in 1993.

If I understand your question, your 1987 and later SBC heads should fit a pre-1986 case without problems. Be aware that there may be some intake and rocker cover mounting issues, however.