Charles,
Before you send the engine off to be worked over try first putting in a little diesel fuel and let it soak. The ether in the fuel is a really good solvent and generally loosens them up. Another approach is to do the crocked pot soak in anti-freeze or transmission oil for a few days. Then take it out, dry off and use a heat gun to warm (read that as heat) the case, cylinder, exhaust port area, let the heat soak in so you have to use a kitchen mitt to hold the engine and with a prop on it gently start to turn it over. Once you get it moving regular solvents (or diesel fuel, but don't flip it) will get it loose. Once you get it loose take the backplate off and make sure the connecting rod moves freely back and forth on the crankpin and wrist pin. Many engines got ruined when the conrod wasn't loosened up before running. If it is stuck use the heat gun to heat the wrist pin area. Let us know how it goes.
Best, DennisT