Go out to your truck and look at the back of the door jam on the drivers side. There should be a sticker that has everything you may want to have to know.
Your Truck is a 1500 which is a half ton. The 5.3L V8 is only available in the half ton. A 3/4 ton could be a 2500HD with a 6.0L V8 or the 6.6L Duramax Diesel.