FROZEN/STUCK low miles motor, HELP!

I had a seized '65 273 engine that had sat outside and got water and leaves in it. Tried all kinds of fluids w/ air pressure with the heads on, soaking for weeks. I tried WD-40, diesel, DOT3 brake fluid, gasoline. Have also heard of using plain water, PB Blaster, coke. Diesel seemed best (or kerosine). After pulling the heads, I finally got all pistons out by beating from the top and bottom. The only thing that worked on some was a sledgehammer on a 2x4 across the piston crowns (Hi-Po raised ones), but I think working from both sides to go back and forth is best. I messed up several pistons by breaking off an aluminum corner on the bottom pin support, hammering on a socket extension. It was greasy, so I didn't see until too late. I should have let the engine soak in diesel for a year. Might have messed up the ring grooves on the other pistons, but that engine requires an over-bore anyway. At least your Slant Six pistons don't cost @#!@.

I have no idea why your engine would turn over, then be seized in a few months in a garage. Maybe a coolant leak caused corrosion. Even with water and leaves in mine, the only corrosion I found was on the cylinder walls and top of the head. Everything in the lower end was fine. It seems to get a permanent protective coating of oil over time.