Back Space: Front v/s Rear

[jim-bob]

...I'm changing wheels and tire sizes on my 88 Silverado from 15 to 17..I'm choosing the back space and OffSet based on another truck( I put only his fronts on my truck and they fit perfect filling up the wheel wells like I wanted without touching anything)..The other truck was not in the shop, just the whl/tires. We just ckd the fronts which I thought was the main concern)...It was mentioned later in the week (when those whl/tires were gone) that the back space on rear might need to be less than the front in order for all the tires to line up the same with the fender edge..The size I've planned on getting is 265/70 with 4.50 B/S-'0'mm OffSet.. I hope I'm clear in explaining this.
Does this person know what he's talking about?