Depends on if you're talking towing or loading into the bed of a pickup. A 2500 is a 3/4 ton and a ton is 2000lbs. This means that its rated to haul 1500 lbs in its bed. While there is a small margin of safety (your truck wont fall apart if you haul 1600 lbs) its a good idea to not exceed the rated limit, especially if you're trying not to beat up your truck. The HD doesn't make a difference, it simply means "heavy duty chassis" which gives you a few stronger components such as u joints, shocks, springs, and maybe axle. It doesn't, however, usually increase its hauling capacity but check the owners manual to be sure.
which has more towing capacity 2007 tundra4x4 2006 g.m.c 2500hd
16000
3678#
6QTS.
13500
1581lbs
4 quarts of 75w 90 synthetic oil.
1500 lbs. that includes driver anything in cab and load
10 us qts.
With the 3.73 differential gears, 9,900 lbs.
22 gal - shortbed 34 gal - longbed
more then 4 quarts