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.
What did you end up doing? Putting my pan on tommorow. Finally got my oil pump and pickup. Still worried about it. I dont understandwhy the pan has the grove coming up. thought about cutting it and using gasket sealer. but, we will see what it does tomorow.