Here is where it really boils down to what you intend on doing with the truck, what motor is in it, and what gears you have.
31's will fit on a 99 without any real rub issues. But you need the gears and motor to turn 'em, for example a 4 cyl with 3.45 gears is going to be a total dog with 31's, no two ways about it, but a 4 cyl with 4.10 gears might be ok with 31's.
On my 2000 2wd Ranger with a 3.0L, 5-speed and 3.73 gears, I ran mud tires for a little while, but they tend to wear a bit faster than AT tires and I had a lot of driving to do. So I took the muds off and only used them when I was going off-roading (now that I have my choptop, the Ranger sees no real offroading). I picked a rather aggressive patterned AT tire in 235/75/15 and ran with it. For all-around use, that was the way to go, IMHO. I went with something a little more aggressive than the BFG AT tires. Usually runs around $100 a tire to find something with a good bite.
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