Chevrolet Repair: 350, 350 chevy engine, ford f 100

Question
Have a 56 ford f-100 with a 350 chevy engine 1979. Replaced the rear main seal due to leak and leak got worse. Replaced with felpro again and still leaking. Do they make a larger seal with bigger bead and wider? If so where can I get one? No leaks found else where. Checked valve covers dist., galley plugs and cam. plugs and oil sending unit. All are dry. Oil comes from bottom of flywheel cover thru hole.Thank you

Answer
Hi Bob,
I wish I had the opportunity to work on that truck.
There are three things you need to check.
1. Check the crank journal for obvious scratches or wear, which I bet you have already done.
2. Check the main bearing for clearance with plastigage to see if the crank is just moving too much for the seal to compensate for, and
3. Check the drain hole in the rear main cap to see if the oil can get back to the pan.
I assume you are using the rubber lip type seal, two piece, rather than the rope.
I also assume, and don't know if it is even possible, that the lip seal is in the correct direction.
Please don't scoff at me for that...I have no idea what your experience is, and even then, I have seen, and done some things that one would think should never have happened.
But that sounds like a fun project.

There is also the remote possibility of a crack or defect in the block, cap, or crank.

And, to answer the question, I don't know of a place like you asked, but google search for CR, or National seal might get you a link.

Good luck,
Van