There is a compression number in mind that reflects the absolute maximum that is allowable for pump gas, but it is based on the engines DCR(dynamic compression ratio), and not the SCR(static compression ratio) which is only the theoretical compression you have, and what everyone says their engine has when they say "My engine has 9:1 compression", for instance.
The DCR is the actual compression value the engine sees taking into account the camshaft timing events, which greatly affects the engines cylinder pressures and its ability to run on pump gas without issues. It is also usually a lesser value than the engines SCR, but is probably the more important of the two of them when it comes to building an engine that needs to meet certain criteria, such as using pump gas. The highest DCR that can be used for pump gas in most cases without problems is determined to be between 8.1:1 and 8.2:1(based on some piston manufacturers research). So once you start mixing and matching heads and pistons around and stroking the crank, this is a number that should become your target, and not the SCR number of 9:1 or 9.5:1.
You can have a SCR of 10:1 or higher and still only have a DCR of 8:1 or less based simply on the cam you select, so cam selection is very critical for tailoring an engines needs to a specific fuel use. And since cam choices for the Stovebolt may be limited compared to a Small Block Chevy for instance, you may find yourself building the engine around the cam, instead of using the cam as the tool it was intended for. But you can still get where you want to go with your build, so don't sweat it.
