Leaky 350 and TH350

[Guff]

I have a 69 C10 with a 350 engine and TH350 transmission that are both leaking fluid. I know the valve cover gaskets and trans pan gasket are both leaking, but it seems like there must be other leaks as well because ithe truck seems to leak oil while it's not running. What are some common areas that tend to leak on this engine/trans combo? I have a rear seal for the trans so I will replace that if necessary. Aslo, is it possible to change the oil pan gasket without lifting the engine?