I have been towing with a 4cyl. Tacoma auto tran. I bought a new one in 2005.
It towed my 16" Scamp
Sd with ease.
I have to admit it does slow down on some long slow up grades in the Mountians.
The longest trip was about 4000 miles up through Yellostone and back.
I averaged 22 MPG.
That was with a full water tank, dual propane
tanks and a 50 w solar panel
with a group 29 battery
that weighed about 80 lbs.
My only complaint has been the low gear isn't very good for slowing you down on log downhill grades.
That's been remedied in 09 with a grade retard.
I have 78000 miles on it and have never had a problem other than one recall to replace a wire of some sort in the Air Bag system.
My first Toyota PU was in 1976 and I've had many since then.
I don't think you will find a better or lower cost of ownership PU than a Toyota.
My youngest grandson is driving the 76 Toyota and it has close to 500,000 miles on it.