Alot of guys are getting back to UC for many resasons. Equipment is better today and models are better. Older engines if treated right can be alot of good fun. To free that old puppy up I will list a few things you can do.
1-Shoot lots of air tool oil into it and let it sit.
2- Best tool is heat gun used for monocote or similar. An old sock help you from getting burned. Heat the crank case and cylinder till engine gets real warm. Apply more oil and reheat. This should get things moving. If engine starts turing shoot in some alcohol and drain and use more oil. Remove back plate and clean with cuetip. If engine is fairly free skip this part as rear gaskets are hard to find and make. Frank Bowman makes gaskets for alot of engines.
3-BE PATIENT and don't force the engine over. Those con rods are hard to get. good luck. Dan