I'm wanting to put a 15x10 rear wheel on my 94 s10. i cant find anyone that has done this with a stock rear suspension. I have seen it once on a tv show called trucks, but cant find any info. I just need to know the backspacing and tire size. Thanks for anyones help  

put it up on jack stands at all four corners.. so it is level... with jackstands under the rear end so the back of the truck is up and at ride height..

pull the tires off the back..   take a straight edge  and a tape measure and start figuring out how much space there is...   this is how everybody does it...  sees how much space there is between the inner and outer fenderwells..