In 2003 I moved my parents 35 miles to a farm. I moved everything they own with my 89 Ranger pulling a 5x8 utility trailer. With my stock axle, which was a 3.45, it was great. 2500 RPM at 65 mph in 5th gear, 3000 RPM in 4th.
The truck has a 2.9L V6, 5 speed mazda trans, and an open 3.45 diff with stock 14" rims. The heaviest I ever towed was a 1976 Ford F-100 pickup with a towbar. I was going to pull it to the new place with the ranger, but when I pulled it around the neighborhood it scared the crap outta me. The ranger would have had the power to do it if I took it easy and didn't floor it and strain the truck, but I had almost no braking ability and even creeping around a corner it felt like it was going to rip the axle out from under the truck, like it was bending the leaf springs sideways as the F-100 was trying to go straight when my ranger was trying to make it turn a corner. I ended up towing it with my dad's old 1979 piece of Chevy because even though it was an underpowered turd with a 250-6 and a 3-on-the-tree, it was a bigger truck, beefier leaf springs, more powerful brakes, etc.
At highway speeds, the most I've ever towed was this setup here, the 3500 lb camper plus 7 or 8 hundred pound ATV in the back. It did ok, not sure what my "zero to 60" would have been though because I babied it, never got over half throttle. On the hills, I purposely let the speed drop down til I was able to use 3rd and only give it half throttle or so. People probably thought I was towing with a 4 cylinder but I was just taking it easy on the truck because it was a hot day and my water temp gauge doesn't work.