440 Fender Well headers ?

the strenght of your unibody isn't as much as a issue as the performance of the headers...

from my ol' Direct Connection manual...equal length primaries, around 33" long for optimum performance

I had a set on my fenderwell headers on my first Duster (Black w/Missle scheme pictured below)....in 1976...tubes veried more than 12" in length and some were over 50" long...and couldn't run much bigger than a VW tire on front.....they sucked!!!