is it possible to squeeze a 31 inch tire up under my stock 03 S-10 pickup? if so is there any rubbin. i was thinkin about puttin 31x9.50x15 inch swampers under it.  

You will prabubly have tire rub. Especially when turning. What size do you have now?  

right now i got 235/70/15 which is about 28 or 29 inches tall if im not mistaken.  

Is that on a 4x4 S-10? Poor 4x4... (kidding)  

yeah it is on a 4x4 s-10. not the zr-2 though.  

Both versions of the S-10 4x4 are the same height right?

That tire size sounds like what I'd expect on a 2wd. I would have expected 235/75R-15 not 70R-15 on a 4x4...

the z-r2 offroad suspension package has 31x1050x15 inch tires but the standard 4x4(the one i have) has 235/70/15 tires.  

they should fit fine i have a 91 s10 blzr with 235 75's on it and they have room for more.  if you leave the tires on stock rims they should fit fine but maybe find that size of tire in an older worn out no good one and have someone mount it on a rim for you and air it up and check it out.  keep in mind that  the new tires will be bigger than an old one with no tread and the big lugz