[twinmill28]

I tow a 28 foot travel trailer with the deuce---drove from Ogden, Utah thru Vegas to Phoenix and on to the panhandle of Florida this summer. Truck and trailer weighed in at 14,400 pounds--so I was running a little heavy, but we were moving and living in the trailer for a month.
The deuce doesn't like pulling the trailer thru the big mountains, we regularly camped in Utah pulling roughly over 6,000 pounds loaded for camp, but it will still do it respectably if you slow down thru the passes; the worst pass saw me doing 20-25 to get over and that was going to our regular campground. Try running any faster and trans & engine temps start climbing rapidly.
Driving from Utah to Nevada in the middle of the summer (end of June) pulling the heavy weight was a bad idea, the truck ran hot and made for a long day of driving thru the desert. We had to drive between 45-50 to keep the eng./trans temps down, and ended up breaking a couple of exhaust manifold bolts by the time it was said and done. We did learn you can still run the a/c even in those temps and it made no difference to the deuce--just killed mileage even more, but who care's--it was freakin' hot!
That road trip saw us filling up at every 150 miles, maybe a couple more if I really wanted to see empty on the gauge. Total road trip was over 2400 miles, so do the math on what we paid in gas! Averaged 7 miles to the gallon.
I tried running a programmer when we first got the trailer, but didn't like the way it made the trans shift, and the increased power brought on increased temps. Turns out that just running premium fuel for pulling is all you need.