350 for torque/mileage

[1972GMCsierra4x4]

This spring I'm planning on tearing down the 350 I have in my 72 K-2500 and building it to be more of what I want. I'm looking to get the best low end torque/mpg combination out of my motor since I may be driving the truck as far as six hours to college in a year and a half. I'm looking for suggestions and what you guys have done with your trucks.

The truck is currently set up with:
350 short block from Oreillys with 600 cfm edelbrock, eddy performer intake, oversized air filter and cast iron 62cc heads (casting #468642)
2" dual exhaust with glasspacks coming out of factory manifolds
4 speed with granny 1st and np205 transfer case
D44 front and D60 rear geared in 4:56 with 245/75/r16 Bf goodrich T/As

The truck will be getting:
650 eddy thunder series (maybe)
Roller rocker arms and the things needed for that conversion
Different cam
Long-tube Headers going into 2 1/4" exhaust with flowmasters
3.73 gears with a gear vendors overdrive/splitter (eventually)
All terrain tires sized in 265/75/r16

Right now my motor has a 9:1 or 10:1 compression ration, depending on the pistons Oreillys installed. My question out of this is a good cam to go with the combination I'm going with. I've been told a thumper is not always a good option but I have seen in some cases they produce really good low end torque and good mpgs. I don't have much experience with cams so that a big problem right now.