I have mentioned this before and it should be checked before you conclude the rear main needs to be replaced.
The crank shaft flange that the flywheel bolts to has two or three holes in it other than the bolt holes which the crank shaft bolts go into. These "other" holes are supposed to have alignment pins in them which allows the correct allignment of the flywheel. If the pins are not in the crank holes, the bolt holes can be used to align the crank so consequntly the pins are left out by some rebuilders. If the pins are not in the holes, those holes go through the crank flange into the bottom cavity of the engine. When running, the engine will "pump" oil out of those holes, throught the flywheel and right onto the clutch and it will run out of the hole in the flywheel cover.
I had this happen to me. Unless you know for sure the pins are in the holes, I would not assume the seal has gone bad. I would check the for pins. If you need pins, you can get them at a parts store. Do not cut off bolts and put them into the holes. Use pins and they will have to be driven into the holes. I did this and it solved all the problems.
I also put in a new seal before I found the pins missing.
Good luck!
