Rear Main Seal leak on my 72 dodge dart

I had the same problem.
I took off the rear-main cap and inspected the surface of the cap and block. Put yourself in the engineering mindset and strive for an ultra flat mating surface(I stared at mine for a few minutes). If you look close enough you might find extremely minor "burrs" or extruding peices of cast iron, especially on the edges. File them down very carefully with the intentions of achieving an extremely flat mating surface to the upper cap.
Also use rtv clear insted of rtv black or grey.
Inspect that cap closely and the mating surface. Take your time and try experimental locations to put that sealant along with the service manual locations.Try to imagine the oil at pressure and where it will be attemtping to seep into. clean all surfaces with mineral spirits or the like.
I offset my seals.
Do not worry so much about the sealent in the engine, you have a filter and it shouldn't be a great amount if you apply it right- wipe the remaining off before installing the pan.
Use spray adhesive to keep the cork in place and try to buy a better quality gasket than cork. I used racing gaskets from Dvorak machine in Gainesville, FL. He might also walk you through this process and supply you with everything you need, as he did for me over the phone.
I blew my seal on the way back from a show, tried this new method and it has been running leak free for a thousand plus miles and a trip at the track. Hope this helps.