before you buy tires, I recommend you bolt those wheels on and cycle the suspension all the way up and all the way down, at both extremes of steering to make sure the wheels do not contact anywhere, and leave room for the wheel-weights.
If they do NOT have the same centerline as the factory wheels, and the same diameter tires, then your scrub radius will be affected. Usually the car will tend to wander,as it grabs ruts or runs up the edges of longitudinal low areas in asphalt roads. When this happens,as the parts age, the toe-in will go towards zero or even to toe-out,and there is your wander.
The factory 5.5 wheels IIRC were a 2.75" or 3"bs to achieve a zero-offset. On an 8inch wheel, zero offset would be 4.5"bs.
Te factory ride height is unaffected by the actual altitude of the car. It is a relative measurement between the inboard and outboard ends of the lower control arms. So theoretically, you could put any height wheels and tires on there, and it would only affect the scrub-radius, as long as all 4 tires are the same.
If taller tires are installed in the back, or the rear of the car is lifted, this affects the caster to a small degree.
If you add or subtract significant weight to the front end after an alignment, this will affect the ride height and the camber.This includes jacking up the rear, which shifts weight to the front.
So the best alignment I ever did to my car was to have everything finalized and I installed 180 pounds in the my bucket.
