That groove in the back is my problem. I thought about hammering it flat but I'm guessing it adds some strength. Even with the LA gasket it wanted to bunch up. there should be an inverted groove on the rear rubber seal that matches the pan.
That is exactly why I trimmed the rear gasket to fit down inside the groove on the main cap.
A pair of scissors and 1/8 or so off each side of the OE LA rubber style worked perfect.
I do think I remember trimming off the stubs that normally go down between the block and main cap of the LA motor in the little rectangular holes.
