Steve,
A leak at the rear main
area may not be from just the seal. Some SO's have main bolts whose heads protrude and cause a gap at the gasket and pan area. This is made worse if you have a windage tray. Member Jim Reiss went through extensive work to discover the bolt head problem on his.
Also, the cap drain may be outside where the gasket contacts the cap.
And finally, you may have a wrinkled pan rail or tray causing leakage. If you search
oil pan threads here, there is extensive info on how I and others dealt with this problem. For instance, Jim and I had waterjet -cut pan rail stiffeners made (using a gasket as template) to allow more even clamping by the pan bolts over the length of the pan. Straightening the pan rail and even filling the flutes in it (to get a FLAT surface with more contact) is discussed.
Bottom line, do some reading first. Like Pat said, try to isolate the other sources and see if it goes away. Then I would probably pull the motor to make a definitive fix. I don't say that lightly, I know what a PIA that can be in a KMS.
Note: I would not block plate the pump. I'd pull it and carefully re-gasket it. Running an electric is fine-
to feed the mechanical-not as a solo fuel source.