I had a friend with a S-10, ext. cab. He never pulled with it, so I can't tell you the tow rating. On Chevy's website they claim a max of 5700lbs for the 2WD. That is with the correct hitch of course. It did OK off-road, although he beat it up pretty badly. As I recall, he had a few problems with the HVAC that were cleared up under warranty.
As for the ZR2 Blazer, I had a GMC Jimmy (not ZR2) that was 2door. Although I like 2door for it's added climbing and off-road ability. But with the short wheelbase it made it really squirrely on wet pavement.
Also, make sure you are getting one with a posi rear. I'm not sure if all of them came with posi rear standard.
Other problems or things to look out for. See how you can live with the strange pillar design. This design makes visibility a bit tricky. Likewise, the rear mounted spare reduces rear visibility somewhat and become a source for squeaks and rattles as my Jimmy had.
Like I said, my friend drove his into the ground (dumba$$). That truck went through several accidents, bad clutch, bad tires, and everything. So... beware you're not buying from a kid like this. (his is totalled BTW beyond repair.)
Always liked the BFG All-Terrains, but they will make some road noise.
HTH
Good luck.