That will get you the compression ratio, but it still doesn't tell you much about the engine components used. A borescope would help some more.
If it were just a stock rebuild I'd say fire it up, you know roughly what you've got. But the more modifications that have been done the more specific the tuning has to be and the wider the range of possibilities. For my time and money, pulling the heads is worth while. All it costs you is a set of head gaskets, and you can inspect the pistons, bores, get a look at the top ring, the valves, head chambers, etc. That's a lot more than just knowing the compression ratio and taking a look with a borescope. Same for pulling the pan, you get a look at the whole bottom end and all it costs is a gasket.
I wouldn't do all that if I knew the shop that built the engine, or the guy I bought it from. But on a completely unknown engine? Especially on a forced induction build. A few gaskets now will be a lot cheaper than replacing engine components if something goes wrong later because something was assumed.
