You have manual hubs ? If so you can just unlock the hubs when you don't want to have it engaged. Or if you get a selectable one it doesn't matter. But a front locker can make you truck experience heavy understeer when it working since all 4 wheel spin at the same speed.... plus it's harder on the axle shafts....
I wouldn't think you'd really need one unless you are gonna run some smaller tires and start trying to actually flex that thing....