I had a setup just like yours except I had an auto tranny in it. It towed OK, but just barely. I found that when I got into the hills, it ran out of power pretty quickly. It did work however. One thing that hasn't been mentioned is brakes. A half ton truck pulling a 1k to 2k lb trailer with a 3 ton tractor on it, takes awhile to stop. Make darn sure your trailer has real good brakes on both axles. Test out the trailer brakes before you put a tractor on it. I can't emphasize this enough. I had to make a panic stop one time a few years ago with a loaded trailer behind me. I stopped in time and narrowly avoided an accident, but I was amazed at how long it took me to stop. It was a greasy shorts learning experience that I don't care to repeat!!
A 3/4 ton truck won't necessarily tow any better, but they have much bigger brakes. For me, that is reason enough to do all my towing now with a 3/4 ton truck, and I check my brakes often /w3tcompact/icons/smile.gif.
Corm