Here is some reference information to get you pointed in the right direction.
Offset: The distance from the centerline of the wheel to the mounting face of the wheel. The offset
can be one of three types: positive, negative, or zero. Positive offset means the mounting face of the wheel is toward the outside of the wheel.
Negative offset means the mounting face of the wheel is more to the inside of
the wheel, like a drag racing car rear wheel. Zero offset means that the mounting face of the wheel is even with the centerline of the wheel.
Backspacing: The distance from the inside wheel rim to the mounting face of the wheel.
Width: is the total width of the wheel, measured between the inner and outer bead mounting surfaces.
Hope it helps,
Jacko