I have the fake welds with 4.5" backspacing... I wanted room for my KYB tubular gas-pressurized quads (they provide a bit of torsion effect, unlike the stock quads, which are basically just dampers), and it's barely enough room... They're 275/50R15 DRs... They're flush with the fender lip...
I think 5.5" BS would rub bad... On my setup anyway...