I ended up buying a brand new LS2 corvette pan after having Heidts tell me it would fit. As you and I both know now, its doesnt. After spending a small fortune on the brand new pan, I just notched the crossmember to make it work instead of going through what you went through. Have any pics by chance of where the pan ends up in relation to the rack, and also the crossmember on the back side?
Do you have a MII Heidt clip or a superide? If it's a superide I had to raise the mounts about 1/2" to clear the rack. All i got from heidt is "it should fit". It's pretty obvious Heidt has never installed a LS motor into their clips with a power rack. Can't move the rack down per heidt because it messes up the tierod geometry.