Offset!

Here is TireRack's Offset Page. It explains what Offset is, but it doesn't explain how Offset is measured. I am looking into buying a set of 5ZIGEN 5ZR wheels for my Fiero and I want a good stance. I will Display what I want, and what I don't want.

I want this stance:
http://www.gpsports.co.jp/fc3s-r-1024.jpg

I don't want this:
http://www.erebunicorp.com/images/au...ustang919f.jpghttp://www.erebunicorp.com/images/au...ustang919r.jpg
Sorry for the small images, but I'm sure you get the Idea.

5ZIGEN has multiple offsets for the 5ZR 18" 2 Peice, but since I have a RWD Car, I'm choosing a set of 18x10" wheels for the Rear. So that leaves me with only 2 offsets on both 18x8"F and 18x10"R:
[list=1][*]+39[*]+44[/list=1]
I need to know how to measure that positive offset for my Fiero, and how to comfensate for the rear wheels being 2"s wider then the front wheels.

Any links or knowledge will be very apretiative.

Ok, I think I'm being ignored. Cause more then half of my posts on 3Geez and racingnewmexico.com are ignored.