Just an update for everyone. I got my new borescope and inspected the cylinders. They are rusty as expected...so are the valves. However, they were not as rusty as I expected... given it has sat for 48 years with no plugs in it. However, I can see a few small piles of what I would imagine is diesel/ATF soaked piles of rust by the piston head/cylinder wall. Wish I had blown out the cylinders prior to soaking them....well, lesson learned for next time. I've also tried more prying of the flywheel and using a 3/4" breaker bar on the crank (hitting the breaker bar with a 3lb sledge)...but nothing has moved. I'm starting to realize it might be time to pull the intake/heads. But...I may try a mixture of 50/50 acetone and ATF....what have I got to lose at this point!!!