There is no seal there.  The stock pulley has some spiral grooves cut in it (looks kind'a like it's threaded).  I understand that these are to not only sling oil back into the engine, but to draw air in as well.  The air flow helps pull the oil back into the engine also.  I know I've looked at it before, but I can't remember . . . does it have a stock pulley or an aftermarket?  Lots of the aftermarket ones don't have the grooves.

If you have a stock pulley my guess would be that you are either too full of oil, or the crankcase breather isn't doing it's job.  We plugged off the crankcase breather on Justin's 74 Super when it had a 1600 dual port in it, and the first time we crossed Monteagle it blew over a quart of oil out around the pulley.  We hooked the breather back up and it never leaked there again.

Also, I remember you showing me that there were extra marks on the dipstick . . . I've thought about those and maybe there is a full mark for when you first turn the engine off . . . then after it sits overnight the oil drains back down out of the oil cooler and you have to use the top full mark.  I'm just guessing there, but that's all I can think of.

If the rear bearing is bad enough to cause an oil leak around the pulley, I would think that everything else in the engine would be in very poor shape.  In the engines I've torn down, that bearing is usually in the best condition of all the main bearings.