Your S-3 tracking straight indicates that the rear axle is "square" with the unibody centerline.
A S-3 does not have a front axle, but the side-to-side difference in wheel base indicates that one (or possibly both) of the front stub axle carriers (aka, spindles or uprights) is not in the correct front / back location. The front / back location is mostly determined by the lower control arm and there is no provision for adjustment. Could be a bent LCA, a bent lower fulcrum pin, a bent front suspension crossmember, a damaged or worn out LCA bushing or an improperly repaired front "frame rail". Or maybe everything is OK and you simply have one of many "dimensionally variable" Series Alpines.
If nothing is bent / broken / worn / etc. and the camber and caster numbers are similar from side-to-side, I would suspect that the front suspension crossmember is "out of square" with the unibody. With the four mounting bolts loosened, the factory front suspension crossmember on my S-V can be moved a surprising amount.
A careful inspection is appropriate, but if nothing is clearly wrong, I would call it good and hit the road.