Just went through the same issues. Built 512 stroker with 440Source kit, Mancini retainer. Replaced the rear main twice after the build due to bad leak at the right rear area. Ended up being the oil pan! New pan that would "rock" on a flat surface. Could even see light from under pan. (put a flashlight under pan on flat surface). Spent about an hour with a board, hammer & dolley to get flat again! So far - so good! Seems like everyone I talk to that has a Mopar has trouble getting the engine to seal! Sometimes ya just gotta be lucky! Jeff