1990 s15 jimmy

i just bought a 1990 s15 jimmy for my 16th bday and i want to know some stuff about it if anyone can help.
1. how big of a lift do i have to go so i can fit a 31x10.5 tire on it?
2. when i get the lift will it interfere with the 4 wheel drive on it bc its on the floor like most of u know and i dont want it to bc pulled down and messed up sitting in the cab.
3. i also want to know about my drive shafts bc im thinking of about a 3inch suspension lift (or whatever is the least i can lift it with 31's fitting without clearence problems)i hear about people having to get new driveshafts for the rear and 4 wheel drive so i would like to know if a 3inch suspension would call for new driveshafts.
if anyone can help i would appreciate it thanks alot

I've got an '89 S10 Blazer (same susp).
I was able to go 31x10.50 without a lift kit. But NO bigger, thats all.
I had gotten a set of used-but-good 31x10.50 Uniroyals for free.
If they didnt fit, so what. They fit very well, only touched very slightly.

Going straight niether the front or rear will bottom-out.
But on a bump & the wheels slightly turned, (like pulling into a driveway that's raised a little) the front tires did touch the rear-most part of the fenderwell. They also touched the frame on lock-to-lock U-turns.

Different manufacturers are larger than others too. . When the Uniroyals wore out, I replaced them with BFGR All Terrain TA's. Those tires have a bigger cleat, and are over an inch taller. They rubbed alot more. And
the knobby edge of the cleat against the thin metal of the fendershield
makes a frightening sound (but not dangerous).

Also you'll change your final drive ratio. You'll only be able to use
the Auto 4th OD gear on the highway above 60mph. It's too sluggish
around town. I had to use 3rd Drive aroiund town.

When those wore out, I went one size smaller 29x9.50
These work the best. Bigger than stock, look good, & my city milage
actually increased a few MPH.