FWIW, I have a 95 K1500 4x4 with 190K miles overall and about 70K on the 5.7L engine (bent a rod @ 123K). Our new to us TT stickers at 5,940 loaded and that's about as much as I'd want to tow with the truck. If I could talk DW into a 'new' truck I'd trade up to a 3/4 ton.
That said we haven't really done a road trip with the TT yet so I'm not sure how it's going to do beyond the fact that the truck takes longer to get up to speed, etc, than when we're towing our sailboat. I'm sure that's partly because the TT is nowhere near as aerodynamic as the sailboat and it probably weighs half again as much as the boat/trailer combo.