Can't figure out this damned oil leak

Understood. Your cover would still be dowled to the block? But, all things considered, you shouldn't be having issues. ATI should still work with stock seal and cover. Mine does. Hope you figure it out!
I agree, as I recall those dowels fit into the front cover pretty tight, no wiggle room. We'll get it working. Like I said I had no trouble with it leaking before this build and it's the same damper and cover.