the problem isn't going to be back spacing or whether he can run a 15 or not. It's going to boil down to offset as well. I have no clue what the factory 15x7 rims had as an offset. However, when I looked into getting the American Racing Teflon Mojaves I ran into an issue of offset. I believe they have a -19mm offset in the 15x8 application. This WILL NOT work with the factory suspension, according to the person on the phone at American Racing when I called. I also called RCD to find out if they knew what offset would work with their lift spindles coupled with the factory caliper and they could not tell me.
Your best bet, call the manufacturer to find out if a particular 15 inch rim will fit or not. Also, the factory alcoas (15x7) had a 4.5 inch back spacing.
Oh and FWIW, with the RCD kit I'm running Eagle Alloy Series 185 in 15x8x3.25 with a -19mm offset. So a -19mm offset will at least work with the RCD kit.
April 7, 2005 the arrival of:
'04 FX4 Level II - 5spd manual...me likey!