I bagged mine, Firestone sport-rite sleeved bags I believe they were. 60 psi with a 1400 lb camper and the truck sat 2" higher than stock in the rear! They are the single best mod I've done to my truck so far. You can get just the bags and manually inflate them as needed (gas station, or a compressor), however I installed a 12v compressor with the gauges and I'm happy I did, its a lot more convenient.
If you use your truck off road, then you will find that they limit the suspension somewhat. Rangers flex pretty well stock, it'll cut it down to about the same travel as most other stock trucks. If this is an issue for you, I can post some before and after pics. LR
'09 Ford Ranger FX4 that gets abused a lot... but doesn't like to swim though.