Yes, 30" tires will fit.... check 235/75/15" tires though when you go looking at price though, nearly all 30x9.50x15 tires are simply 235/75s with a different number stamp. They will fit on both 2wd and 4x4. If you have an 89 or 90 2wd Bronco II, you can even fit 31x10.50x15 tires stock, without trimming. Not so sure about Rangers though (and I haven't tried fitting 31's on a stock 4x4 BII or Ranger...yet), but if you know someone that has a set you could stick on an test out, it might be worth trying.
You may want to see what gears you have in the truck as well (please refer to the chart on the tech pages). My choptop had 3.45 gears in it with 31's and a 2.9.... previous owner tore up the clutch trying to run it like that (of course, I'm not sure exactly how skilled he was at driving a manual trans either as I never witnessed any). I never drove it like that, first thing I did was change to 4.10 gears and 4x4. Second thing I did (after a lift of course) was to fit it for 33's. I've run 30" tires with 3.73 gears and a v-6 (both with a 2.9 and a 3.0) and I'm not sure I'd like it much with 31's or bigger.