We can even take this a few steps further...a bit extreme but something I've pondered on those long tows.

You decide to build your own car, but are certainly not an engine builder. So you do research and find a reputable shop that is familiar with SCCA's rules. You make sure to tell the builder that you want a legal engine. You even go do some further research to verify that the pistons that will be used are truly legal. Compression check is done after, and it's within the rules. Cool, you've got a well-built legal engine. Or do you? Yeah I know, I hear those helicopters beginning to start their engines. And one would hope that the engine builder wouldn't want to ruin their reputation.