Max compression for pump gas iron head

The late 318 slugs are a flat top right? So are the KB167s. Zero deck is zero deck so use the taller pistons and save your poor machinist a few decking passes on the broach. You need to shoot for a quench height of .035 - .045 or so, and a typical composition head gasket will get you there really easy with zero deck.

Also, the KB167 is a little bit stronger than the OEM slug. It's still a cast piston, but it's a really nice cast piston.

Make sure there are no sharp edges in the chamber or on the piston, run a cold plug, pay attention to oil control and you shouldnt have any problem with pump premium.

I run almost 10:1 in my pickup on midgrade with shallow open chambers (Buick 350). Chamber prep helps.