I've tried using the RTV by itself, instead of the cork end seals provided with the Fel-Pro gasket set, but it still leaked. It's so hard to tell where it could be coming from. When the engine is idling, there is no visible leak. Only when driving, when the engine is under a load (with increasing oil pressure, of course) does the oil start to accumulate on the bellhousing. A friend of mine told me that I could have warped my aluminum Edelbrock manifold if the PO did not torque it down correctly. Just looking at the thing, it doesn't looked warped, but I imagine it doesn't take much of a gap for oil to fit through at high temps and pressure. That's why I bought a brand new manifold and valve covers. And yes, I was running a mechanical oil gauge but when the actual gauge began filling with oil, I knew it was time to buy a new one and switch over to an electric one. So I'm pretty positive it's not the oil sending unit.
1979 CJ7/Chevy 350 V8/Ford T-18/Dana 20/Dana 30F w/ Detroit Locker 3.73/AMC 20R 3.73/4" Superlift/3" Body Lift/35x12.50x15 Baja MT's/15x10 Steel Rockcrawlers/Body Tub Liner/Milemarker PE8000