[68protouring454]

i would just miter cut it or modify chassis and run front rails at same width from under the car, i ran into this problem also most of the mandrel guys need 6 inches inbetween bends, thus creating the issue with the rise part of the chassis as most of the time its less then 12 inches you need both bends.
i would miter cut the pieces then weld grind smooth and fish plate on the inside.

p.s by miter cutting it you can jig your upper rail in place, cut corresponding angle on upper rail, then notch tube to rest on lower rail and compound miter cut the upper cut so it lays inward and mate to the upper rail nicely.