So, will 5.9" back space be to little on a 18x9" rim, front of 74 duster w 11.75" factory type brake setup??
Concerned about outer wheel rub on top and sides of fender. Probably running either a 26 or 27" tall tire on front.
6" is pretty much the minimum for a 9" wide rim, but Ive heard of 6" backspace on a 9" wide rim with 275's. I'd guess that you would need to trim the fender lips to make that work.
Also, a 27" tall tire would be a lot harder to fit than a 26", especially if you're lowered.