The only other thing I can think of is if you ran the engine with old gas varnish may seize some or all your valve stems in place. Take you valve cover off and check for bent pushrods. Good luck and please keep us informed of what you find.
I had that happen once on one of my non-Bolts--Got it started for the first time in a lot of years--ran like a Swiss watch. The next time several weeks later it sounded like a John Deere tractor. Turned out some of the valves had stuck from the varnish in that old gas. Ended up replacing the gas tank, due to the amount of crud in the old one.
