Quote: I cut some spacers, 5/8" long from a few old 1/2" bolts and tacked them to one wheel. Perfect. The hubcap fit like factory.
That is the best idea so far, the full weld bead prevents any rust staining.
I saw a related retrofit on teh Chrysler 300 site wherin a guy welded a 14" rim-ring to a 15" wheel (to use 14" wheelcovers with 15" tires). My concern with that idea is that unless you do 360° of welding to the wheel (which is a lot for a DIY person to do to a wheel), it's gonna bleed rust eventually.
