Had engine overhauled out of state and after about 500 miles it developed an oil leak at the gasket interface of pump to engine. I have tried 4 times with OEM gaskets and they immediately fail. Used two different torque wrenches, what am I doing wrong? Could it be a pump problem? I can't find anyone in southern Ohio that knows anything about this engine.

Are you talking about where the accessory drive bolts to the engine or the plate on the bottom of the accessory drive where the oil pump is found. Assuming it is the accessory drive to engine, have you inspected the seating surfaces to make sure they are flat. It would be easy to drop the drive and mess up the seating surface, since it is made of aluminum. Are you using any kind of sealant when you install these two gaskets and you slide the accessory down to tighten the cam belt. If the surface is messed up, when you slide it down you could be ripping the gasket. You should also post your question over on the OHC forum because there is a lot of knowledge over there specific to these engines.