Check out <a href="http://50chevy.freeservers.com/Suspension_Widths.html#Suspension" target="_blank">this link</a> for some common widths. Backspacing on your wheels is going to play a factor, but as long as you know what the backspacing will be you'll be fine. I've got a stock '89 S-10 4x4 rear end (58"?) under my '52 Suburban (same chassis as the pickups) and with 4" backspacing on P235 75R15, I only had about 3/8" clearance between the tire and inner fender well. Forgot to take tire bulge into account when I measured.
A couple of 3/8" spacers can be had for cheap.
If you don't know what wheels you'll be using, you can narrow and widen the track width by specifying the backspacing on your wheels when you buy them.
[ August 26, 2002: Message edited by: Stinkin_V8 ]</p>