Any idea of how many miles are on the engine? If all the suggestions above don't correct the problem and the engine has lots of miles on it I might be the slop in the timing chain. Of course you'd have to tear into the engine to replace the timing chain but it might be a last resort for you.
I doubt if any one would stash 2 junk engines in a trailer. They probably had worth and value to whomever originally decided to keep them. The suggestion of being up front and asking if you can check them out for damage. I'd bet he'll have no problem. If the blocks are shot them offer him a...
Try warming up the gear to 200f if there's no burrs on either the cam snout or the gear. Your doing fine! Take your time, lots of lube and it'll all come together.
Dan
When I was a kid I worked part time after school for a guy that had an A100 van with nothing but a heater/defroster and one seat. He used plumber strap to anchor a milk crate upside down to the passenger side floor and wired a old cushion on top. That was my seat as we drove around town...