Is overspray on cylinder head ok?

wtf are you on about?

yeah there's two or three that aren't uniformly polymerized, but given the rest of *waves hands broadly* this i wouldn't be terribly concerned. they're ball & cup on stock 273 adjustables, the chances of them being mismatched is small. very small.
From everything that I saw and read about the engine, I wouldn't start it without a closer inspection. I saw a couple of pushrods that looked crooked.