1pc rear main small block oil pan gaskets

[Tom]

I put two new fel pro oil pan gaskets on my 98 in the truck. Both leaked. Got fed up, pulled entire engine to re-seal everything with full felpro kit. Followed the directions PERFECTLY [which happen to match the oem GM manual] with the engine upside down on the engine stand for ease and perfection. Also have new rear main seal, new timing cover....
Anyways finished up, let sit overnight. Next day I put everything together besides the intake, and prelube the motor. Let sit overnight again.

Came out to oil leaking on the floor. Its going past the gasket at the timing cover, literally in the middle of what you'd call the front main seal I guess[the arched part where cover meets the pan]. This is beyond frustrating, to the point I ordered a new oil pan and a mahle gasket this time because I can't for the life of me figure out what else could be causing this? Any pointers or things not normally mentioned in instructions?