No matter what the frame rails do, since the mount is mostly connected to the front crossmember no amount of twisting is going to translate into damage I think. I think you'd have to mount the rad in teh middle of the frame and use it as a crossmember to have the frame twising cause damage.

My plan is to throw some garage door rubber weatherstripping behind the "clamping" part of the bracket and assume that with so much surface area, the rest, (square thing) won't damage the rad at all. Had I built a traditional bracket setup where there is basic c-shaped clamps and no means to apply tension I would have used rubber pads or something, but since I can clamp everything down tightly I don't think much is necesary.

After all that the elbow fits now, and I talked to a guy with a 3800SC and the thermo housing would work. I might not need it but it is good to know it is there.