'92 Caprice wagon wider wheels - questions

Okay, so I've decided I know NOTHING about wheel shopping.

As most of you probably know, my wagon has 15x7 wheels. I'm piecing together a shopping list (most of this is conceptual at this point, but I'm pretty serious about it), and I ran across wheel offset and backspacing. I think I understand the concept (for the most part) but I was wondering if anyone knew if there was say, a table to size wheels?

I saw toomanytoyz's wagon has 18x9.5's, but that's too big to me. I was thinking 17x9, 16x9, or even 15x9. I want the wider tires and wheels, and if I can get an inch or two in rim size, that's great too, but big wheels don't really appeal to me, so no bigger than 17's. Plus large tires seem to get expensive, so that's another factor for me. Not to mention ride comfort with less sidewall and such.

So I guess my main questions are: since I know you can fit 9.5 inch wheels, what offset/backspacing would I need to run:

15x8
15x9
16x8
16x9
17x8
17x9

Those are pretty much the only sizes I'm considering. I love the look of the fat rear tires, but I also want to keep all 4 wheels the same width and size so I can rotate tires easier. Thanks for the help!

Sorry I took so long in answering, I thought someone else would reply, and noticed that no one else did.

Measure the back spacing of the wheels you have now, and add 1/2 of the difference in width. Stock wheels are 7 1/2", so for a 9 inch wide wheel, add 3/4" to the backspace. The backspacing is measured from the pad, where the wheel sits on the axle flange, to the edge of the lip on the back of the rim.

you need to call me and come see my 15x8 Cragers with 255s. I think you will like them alot. I also have a set of factory Impy rims you could try on for size to see fitment, etc.

I'm guessing you are home for the summer now....check your PM for my cell #

I've got my 255 60s on 7 1/2s and they look really good. I am running 205 70s on the front. They are less than .1 of an inch of each other in diameter.

I have a set of 10 inch wide rims, but the make the tire have 1/4 inch interference. I was told that they would fit. Someone lied to me, or had them on a sedan. Maybe if I rolled the fenders with a baseball bat, I could get them under the rear.

Yeah, I've been home for summer since late April.

Got your PM. When I get everything all set up I'll give you a ring. Should be a fun trip.