Not sure if any of that info is here Sealed Power Cast Piston (Carton of 8). All I saw was 1.720 Compression Distance. Not sure exactly how much he took off the head. I think it was just enough to clean up the surface. I'll have to ask him tomorrow.
Man I hate to break it to you... those look like stock replacements. It says "8.5:1 CR" in the specs which can change with a lot of other factors but still means something, and it's not good lol. That 318 is gonna be a turd until at least 2500 RPM, what gears you got in the back?