So I found out today I can get the american racing vector wheels dirt cheap through a distributor at work, but they only offer a 15x7 with a 4" backspace and a 15x8.5 with a 5" backspace. Right now I have 31x10.50s on 15x8 with a 4" backspace. I'm thinking the 8.5's, granted they're 1" less on the backspace, but they are a little wider.

 

Both of those wheels will sit in farther than what you have now.

 

5" is just about stock give or take 1/2". You'll rub with anything wider than a 10.50" wheel and might even rub the control arms at full lock. Spacers are fine but at that point you've invested enough to buy proper backspaced wheels.

 

Go for the 15x7's if and only if you plan to stay with a 10.5" wide tire. If you have any desire of going bigger in the future (to a 12.5" wide tire) you'll need the extra width of the 8.5" wide wheel but will rub on control arms and other places with 5" of backspacing.