Is overspray on cylinder head ok?

Look at the adjusters on the rockers.......Those pushrods are way too long.

Brother, do some research, tear it down, check and measure, re assemble with new gaskets. This may sound like a lot of work, but trust me...it will be a fun learning experience if the engine looks good inside. (It will suck if it needs machining...but at least you'll know).

Ask tons of questions here......Lot's of great advice. @krazykuda has a great engine re-build tutorial (with pictures) to help you through if you need it.

My .02 cents
Who ever painted the engine in my opinion was lazy, all they had to do was put the valve covers on. I've read on here more than once about the pushrods being wrong and I agree. Somebody said earlier for the op to go ahead and run it as is which would be the worst thing that he could do. Going by the pushrods being wrong and the sloppy paint job I would tear it down no matter what. I hope that the op didn't pay much for the engine I don't care if it's a 340 or not, as I said earlier it's had a spray can over haul