How to stop rear main seal leaks
I have worked with early 322 nailheads and one 47 straight-8, so yours should be similar. Some of this can also apply to other engines with rope seals.
Some assumptions: You know how to get to the rear main bearing cap and remove it and you know what a rope seal is. The engine is in the car and the crankshaft is installed.
Do not remove the upper seal. If it is not now absolutely flush take a portion of the used lower seal and stuff in the gap with a suitable tool. It is ok if it protrudes some. Take a 12 inch length of heater control wire, sharpen one end and install it into the groove that the upper seals sits in using a 6 inch length of brake line to keep it from kinking. Using vise grips push 1/4 inches at a time until it shows up on the other side. Install 2 pieces. Cut the wires flush with the block.
For the lower seal that goes in the cap take the piece that is supplied for that engine, bunch it together and flatten it and place it in the groove in the cap. Bunch it some more to make it fit while pressing it into the cap with a piece of exhaust pipe about the same diameter as the the crankshaft journal. Never cut or trim a seal to make it fit. It is OK and desirable if some seal protudes from the cap. (For situations where the crankshaft is out of the engine, remove this seal from the groove in the cap and place it in the groove in the block; repeat for the lower seal.) Fold any stray strands of the seal to the center so they will not get caught between the
clamping surfaces. Install the cap and torque to specs. Remove the cap and trim any stray strands that got clamped. Put some gasket sealer on the clamping surface of the cap. I use an anaerobic sealer. Dribble some engine oil on the seal only until it is saturated. Install and torque to specs.
To seal the groove in the sides of the cap I take some cotton twine coated with some No. 2 Permatex and hammer it to stuff it tightly in the groove using a large flattened nail until it is level with the top.
(sorry about that wormy guy in the last picture --- hard to get good help these days...besides someone has to supervise and take pictures)