Max compression for pump gas iron head

As far as stock pistons go, the 67-69 318 pistons are closest to the deck (.036) 70-71 @ .060, 72-86 @ 056. The earlier pistons work fine in the later blocks. They also are cut with 4 valve relief pockets.

Compression ratio on the 67-69 engines was 9.2:1 from there on it goes down to 8.5:1 until the 302 heads were released in 85 which bumped it back up to 9.1:1.

Personally, I'm running the 302 heads on a '68 engine equipped with a .441 lift cam, duration 218/228 @ .050 lift. No problems on 89 octane.