Everyone that has put a number of engines together has had a leak or two in their builds. Myself included . I had never had a rear main leak until I stated so on a posting here on Moparts. Next build , rear main leaked like a sieve. Don't know why, replaced the rear seal , no leak. Had a oil pan leak, thought it was the rear main on another engine, It was caused by the girdle studs hitting the back of the pan. Ball peen hammer fixed that. That brings me to question if you put a girdle on or changed to main studs in your engine? You can fix the leak, Most repair shops have some snot nose kid doing that kind of work.