ok, i ran some borrowed 31's on a club run a couple months ago and had them on stock steel tracker rims. i thought they were 15x7 but all the info i can find says different. im wondering if it is acually the same width as my rims i have that are 15x5.5 as that opens up alot more rims to me. i have a set of 31's to throw on the truck but i need another set of rims for them as i still need to run street tires.

ive read that some dodge ram and ford truck rims fit as well, but whats the backspacing?

Yes, as long as the center hole is 105mm or 4-1/4" and the lug holes
are 5 on 5.5. As far as the backspacing the stock wheels are pretty
neutral, so probably half the rim width, but to be sure you need to
measure them on a case by case basis

Wild

Most ford and dodge wheels are around 3.5"-4" backspacing.  Most aftermarket wheels will be in that range too for backspacing.

here is a link to all the stock rims that will fit
http://www.zukiworld.com/forum/technical-discussion-beginner-repair/92-sidekick-rims/

i thought that center bore hole had to be 108mm to fit ,

4-1/4 inches is 108mm but the hole only has to be 105 for the front
hub to fit through, if I'm not wrong about the dimension, but I could
be wrong, I'm just going from memory

Wild

np wild you r pretty much the guru on trackkick from what i have read

Thank You, I'm wrong sometimes, but if someone says other
from what I thought the answer is, I go look it up to make sure
I got it right, still learning every day