You can lift your front suspension up 6" without a body lift. You have two options for the front.
One is a spindle lift, which yields 3" of lift, with no change in ride quality. Most expensive, but it is the most favorable option as well. An alignment is recommended.
For the other 3" of max lift, you can pick up some coil spacers or some lift coils. Coils stiffen your ride because they use different spring rates. There are plenty of different heights for coils and spacers, ranging from 1" to 3". When you lift more than 2" with coils or spacers, you might want to look into aftermarket upper control arms to aid your alignment. Keep in mind, that with coils and spacers, you will need extended shocks and new alignment cams, and obviously an alignment.
For the rear, you have different options as well. You can add lift blocks, extended shackles, add-a-leafs, and lift springs. New shocks will be needed to accompany any lift.
You can also add a 3" body lift for a 3" of lift.
31's are preferred with 2.5"-3" of lift, and 32's will have minor rubbing. 33's are preferred with 4.5"-6" of lift, and 35's are for the 9" of lift.
'99 Ford Ranger XLT
3.0L 2wd Stepside
Fabtech 5.5 w/ Bilstein Shocks
32x11.5x15 BFG A/T on 15x10 AR Baja Wheels