On my truck there's a distance descrepancy between the front wheels and the back of the wheel-well -- it's most noticeable when I've got the wheels turned and am washing the truck - been there since day one and my truck has never been hit. You've got to remember that these were pretty much hand-assembled - I don't believe Isuzu went the whole robotic route in assembly as the production numbers didn't justifiy it so there's some variation in measurements. As the parts go on, some could be slightly mis-aligned but as long as the mechanics and esthetics aren't violated, it passes inspection. If the rear-end is slightly to one side it probably doesn't affect the driving or alignment of the truck much - it would be more important in the front as you're cornering, for the two sides to be within a tighter tolerance. In your case the mechanic probably did set the axle assembly slightly to one side - do you notice a difference while driving? A difference in handling? If not, it probably tracks parallel to the length of the car. Just talking out loud.

-- John