I had that issue on my 367 after I allowed a really well-respected engine shop to align hone my block,against my better judgement. Turns out their BHJ fixture, if they used it at all, changed the geometry so bad at the rear mainseal, that the factory seal would only go about 2000 miles before the rubber wouldn't contact the crank anymore, and the oil would blow out in the same location as where you are having trouble. while on the other side, the rubber was nearly worn out. I didn't catch it the first time either, thinking I had made a mistake during the install. But 2000 miles later it did it again. So when I pulled the second seal out, I had a really good look at it, and that's when I saw it. So I went back to my tool box where I had deposited the earlier failed seal, and sure enough it was the same.So I took the problem back to this well-respected shop, and showed him what was going on. And I kid you not, he said to bring him another block, and he would give me a free line-hone. Ok,wait, what about all the other machining? Um,no we didn't screw that up. Despite the truth in that statement, it was ridiculous.
Anyway, I went back to my parts supplier and it turns out a 383 rope seal fits in there with minor trimming, with the sharpest razor-blade in the pkg,lol. But no, the leak continues;just less profusely. I am on my third rope-seal, cuz it seems they are really tricky to install, and they are a little fat now that my block is all messed up back there.And yes, my bellhouse had to be moved up to recenter the tranny pilot to the new crank location. And all the Housing bolts had to be relocated as well.
Since you are having similar issues, I suspect this is also your case. The ropeseal is the easy answer, but it is not the best. Mine continues to seep and dribble. Oh yeah, I should mention, that with a new ropeseal and a 4 psi pressure test, it does not leak at the time of the install. The leakage begins later.
