If there is any way you could see buying a diesel, you won't regret it when towing. My first TV was a 90 Chev 3/4 ton that I upgraded to a 383 engine. I used to tow a 20' car hauler with it. Loaded it was about 7500 lbs. I burned up the transmission towing at 55 mph. I then bought a 2001 GMC diesel. The old LB7 engine only had 300 hp and 550 ft-lb torque, but it would accelerate going up hills with the same load. I towed across country 6 times fully loaded without a glitch. Now I have a 2014 Ram 3/4 ton diesel with 370 hp and 800 ft-lb torque. I pull a Prowler 24C with it and averaged nearly 12 mpg over and back across three mountain ranges and speeds up to 75 mph (1700 mile trip earlier this month). Yes, diesels are more expensive, yes, their maintenance is a bit more expensive (fuel filters, 3 gallon oil changes, bigger tires), and yes, you gotta plug them in at night in a cold winter. But, for towing, you can't beat a diesel's torque.
Just my $0.02, adjust for inflation as appropriate...