Pull the valve cover and spray down the valves really good too. "Lightly" tap the top of the valve (not the rocker arm) to see if the valves are loos in the guides. I swear by KROIL for a penetrant. I would break the motor loose and be able to turn it over by hand before using the starter to turn the engine. Put in 1/2 Dextron II and 1/2 engine oil to prime it and get it started on. The detergent in the tranny lube will help and also soften the seals a bit. I don't drive the vehicle with the tranny oil, but I run it til hot and without loads. I think it helps loosen up rings too.
