Pat, re: mileage.
That 39 mpg is uncharactistically poor mileage for me. In the winter I usually get in the low to mid 40 mpg range. During the warmer months (April thru early November) when I don't have snow tires on all 4 corners and don't burn winterized fuel, and get around 50 mpg. I've gotten as good as 64 mpg when I watch my right foot - done that for two tanks back to back, but it takes some concentration to press gently on the go pedal. Here to Dallas or here to Washington DC without stopping for fuel is possible.
I can tow up to around 3,500# gross, but like to keep it under 2,000# for less wear and tear.
No hybrid for me, it's a VW TDI Wagon. I have done some modifications to it, more for performance than for MPG, but the mpg did increase a tad vs. stock, about 4 mpg over stock.
Reflashed the computer (Rocketchip III), added larger injectors and changed some of the intercooler piping. That increased the hp and torque from 90/155 to 130/300. I didn't like the way the car stopped with 3 guys in it, hunting gear and a small (<1,000# gross) trailer, so I changed the brakes to larger brakes from an Audi TT Roadster (both front and rears). I changed 5th gear ratio to lose about 400 rpm on the highway and at the same time I added a Peloquin torque sensing differential. Then because of the brakes I had to go to 16" rims. There are more modifications done, but those are the biggies that pertain to mileage.
I use it for the majority of my driving where I don't need to tow something heavy, or go off-road. There's only about 4.5" of ground clearance, so even driving on some construction sites is an iffy propositon - I'll take the truck then.
