I think that all the trucks made after 1998 come with ABS.
But if you want to be sure, find yourself a gravel road and brake as hard as you can. If you feel some pulses on the brake pedal, and if the truck turns while braking, you have ABS
Huh? If you want to know if your truck has abs brakes, do a power stop and if you hear bzzzz bzzz bzzzzzzz like a damn robot then you my friend have abs. Usually when you tell fockwad at Murrays or Autozone what type of truck you have they'll give you the right rotors. Also, do you have a 20''/22'' combo? make up your damn mind!!!
Start your truck, put it in gear and let it inch forward as you slowly apply the brakes. Try to get to the point where the brakes are just between clamping down and not holding. You'll reach a point where it starts to pulse. Like a bubbly farting noise.