Pan gasket for 360. What one works best?

everthing has been done 3 times. i have less than 150 miles on the motor since the first rebuild. I have replaced the cam twice because a lifter was up in the wrong place on the second rebuild. but the cam seal has been replaced all three times, once by the machine shop. al the plugs on the back of the engine have been checked, everything is new and freshly paintedand can find no sign of a leak on back of engine. crank replaced and new rear seal replaced three times. i have checked the back of the intake around the heads, the valve covers the oil filter and the distributor. like i said everything is new and clean and there is on oil leaking down the engine anywhere. what else could it be? thanks for your replies