My cheapo spacer showed up and I did some test fitting. The roller P255/60R15 setup will clear everywhere. Shown is the tightest spot, which is the forward end of the upper control arm upper pivot bolt with the tire turn to right lock, about 3/4" of clearance.
On the 17" rim setup, the rim will clear everything but when I put my tire emulator (sounds more professional than 2x6) on it hits the upper pivot of the spindle. I need another inch of spacer, which is going to get real close to too much on the outside of the wheel well. Oddly enough, even though both the 15 and 17 inch combos I want to use are P255's the 17" tire section width is a half inch wider than the 15" one and that half inch is making itself felt as it is a very tight in there using this wide a tire.