Chevrolet: 350 Chevy engine, chevy engine, seal area

Question
I have a 1979 350 chevy engine that has a rear main seal leak. We re-placed the seal and the leak was worse. We pulled the trans back to see if the oil galley plugs and other plugs were leaking. We did not find a leak. We cleaned everything off and started car and waited to see leak. Upon first notice of leak we shut off eng. and it looked like the main seal was leaking. We again re-placed the seal, but the leak continues.No valve cover leaks or leakage from above. Any other ideas.We know the eng. was re-built but do not know what was done or by whom. HELP

Answer
Usually a rear main seal wont leak when the engine is running. It leaks after the engine is off for awhile and all of the oil drains back to the pan.
Unless you are damaging the seal when you install it, it shouldn't leak unless ther are nicks in the seal area or on the crank. There should be some sealer on the rear main cap to stop oil from seaping out between the cap and the block.
I would suggest only using a GM or maybe a Felpro seal.