I know I come to this discussion late, but I pull our T-1550 with my 2009 GMC Canyon. It's a 4 cylinder 5 speed with a 2100# tow max, but the automatic in the same truck has a tow rating of 3100#s. From what I've been told, they rate the standard lower because they think too much shifting is bad. When I travel, and a lot of it is on interstates, I travel continually in 4th gear at just under 3,000 rpm, and find the truck does fine. The only options on it when I got it was a locking differential and a tow package. The tow package comes with a bunch of stuff, but includes a lower rear end gear. It also is ready to easily hook up a brake controller, which I did before we went to look at the T-1550 two weeks ago this past Saturday.
I have lots of experience towing loads with this truck, as we travel far and wide with our classic speed boat behind it, and I learned early on the way to do it was to travel the interstates in 4th gear. Mileage isn't great, but it's not below 15 either.
Another couple years will probably see us with a full size pickup. In the meantime, my Canyon does great!
2009 GMC Canyon with factory tow package & new fangled brake controller
2008 Subaru Outback
1983 Sunline T-1550
Image to come as soon as I figure out how to flatten a pic!