Two things I have not seen mentioned here:
First, check the crank flange where the flywheel is mounted. The crank flange on these cranks has three pins in the flange to correctly align the flywheel. On occassion, those pins can be left out, maybe not all of them, but it takes just one. If so, it will fool you into thinking you have a rear main seal leak. The holes for the pins go straight through into the bottom of the engine. The oil, under pressure, will come out much like you describe.
Second, if you have to replace the seal, the neoprene seal has never been recommended for these engines. Rope is best. Drop the crank, turn the crank as you feed the rope through trying not to pull too much. Cut each end of a little long and apply a small of gasket sealer on the ends when you put the cap back on. I use a paper hanger's seam roller to roll the rope tightly into the bottom cap. You can't roll it too much. Cut it a little long for the sealant to go into the top rope and the bottom rope.
This happened to me and it took awhile to figure it out. Just my opinion, I think Fel-Pro makes the best gaskets out there.
Good luck with with solving your problem.
