rear main seal oil leak

[haplo]

 Help  have a 1974 360 stroked to a 417, oil leaking at rear seal, droped the oil pan seal is in correct.   any thoughts?

[Follicly Challenged]

Very frustrating problem, my condolescences.

Anyways, just a thought, one more possibility to check next time you're in there, is the groove that holds the seal in the block "centered" ?
I've seen blocks where the groove is actually slightly staggered to one side, whereas, when you're looking at the seal compression against the crank in the block, with the rear cap off of course, you can actually "SEE" the lip contacting and compressing more on one side than the other.
Did the same thing as you 4 times before I caught it !
Really frustrating !

The "fix" for me was to stagger the seal across the parting line about 1/4" and use the cap when re-installing to drag the seal into contact on the offending side.

Just something to check, hope you find the problem, I really feel for you ! Good luck !

[Bullitt-]

once I thought I had a leaking rear main, 2 professional mechanics told me so. Later I traced oil to rear of intake where gasket seams at corner were not together.

[Chryco Psycho]

I had a small leak at the oil sender at the rear of the block that seemed to be  the rear main

[JCWCuda]

Sometimes the sending units will blow oil right out of the top and it then runs down the back of the block

[daves70]

  Could be any of the above fore mentioned. Could even be a valve cover leaking at the rear and running down. It's a process of elimination! 

[R/T]

I had a small leak at the oil sender at the rear of the block that seemed to be  the rear main

I had a 360 in a 1977 road runner and if you nailed the throttle hard off the line it would snap the oil sending unit off. New motor mounts and it would still snap it off so I finally built a solid motor mount  for it after that it would lift the front tires