Pan gasket for 360. What one works best?

Its either the rear main seal, the pan gasket, or something is leaking from the top of the motor.

The problem is that everything runs back there. Have you used the same kind of rear main seal each time?

Is it coming out the freeze plug behind the cam?

Are you sure nothing is leaking on the top end? One of the heads, or maybe the seal at the back of the intake manifold (are you using silicon or cork there)?

Bad O-ring on the dizzy?