There's a lot more to it than just "10.5:1 with iron heads". If you had any factory-style LA head (besides #302 casting) they would have open chambers and you wouldn't be able to run much more than 9.5:1 without getting detonation. BUT since you are running a closed-chamber head, if you build the engine to have proper quench distance between the face of the piston and surface of the head (.035-.050") you can run higher compression without pinging on pump gas. It DOES work, I built an engine myself to try it and it all came out perfectly exactly how I thought it would. Again 10.5:1 engine with iron heads and small RV-type cam, and runs on mid-grade pump gas. And the only way I can get it to ping is by hitting the gas in top gear at a slow speed.
