Ask the "honest" seller what cam he used.
Could be stock, could be way overcammed, could be a "thumper" that's all noise and no balls. Could have 3 wiped lobes for all you know, having never heard it run...
You can get an idea of the specs by putting a dial indicator on the rocker, but that'll only get you into the ballpark.
If I could tell you exactly what was inside an engine without cracking it open, I'd be a rich man. I'm afraid if you want to know for sure, open it up.