I had the same problem with my 408C and the stud girdle and Moroso pan fitment. In order to make the rodcaps clear the main girdle I had to hard shim the girdle up off the main caps. It made the pan hit in the tapered area you addressed. I ball-peinned the pan in that radius and actually ground the outer rail of the girdle to make the pan fit. After hours of work it weeps from one of the pan bolts in that area. I am going to pull the pan off and replace it with a Canton pan, I don't think I need the girdle with the 4-bolt D2AE-GA block.