Stock Blazer wheels are (I think) 15x7 +51 offset with 6in backspacing

 

Ohh im glad i found this thread, i was confused also. So back spacing and offset are kinda related? if you have a higher backspacing then you will have a lower offset, because the mounting plate gets moved back from dead center of the wheel? or is that backwards? either way that would make sense to me.

 

This:

The relative position of the inside face of the center of a wheel to the rest of the wheel is measured two ways.

The offset measurement refers to the distance away -- either outside or inside measurement from the center plane of a wheel. This offset is usually a small number and may be negative or positive depending on the direction of the offset -- towards the outside face or inside face of the wheel.

The backspace measurement is the distance from the inside face of the wheels' center to the edge of the rim (or at the bead) on the inside of the wheel.