Depends...
Does this truck have 5 lug wheels? If so, the rear axle is pretty light duty. Also, what is the axle ratio? The light duty 6.5 will pull pretty well with a 3.73 but if it's 3.42 not so good.
I used to pull a 6000# horse trailer with a LD K2500. Same engine but heavier, 4WD running gear. Also, the horse trailer is probably a little more aerodynamic than the TT. I got 12-14 mpg on the highway.
YMMV
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510