If it were me and I had money to spend I'd get a AFE intake, Turbo back exhaust (no muffler), Edge Attitude w/ the Hot code unlocked and a Sun coast transmissions Converter at a minimum and a whole trans if possible. I'd run on 285 70 17s on H2 wheels (cause they are cheap). That's my .02 cents. When you've got it built i'm sure we can arrange a little tug o war between the cummins and the duramax. I'd also invest in some tire rod end sleeves so that you can launch hard in 4wd without snapping one. 10 to 12K lbs is nothing for a 3/4 ton diesel, they'll pull that all day long up any hill there is in FL. I'd say with that set up you'd be getting about 18 to 19 mpg. a Co worker gets an honist 18 to 19 @ 70 mph with AFE, turbo back exhaust and the 90 hp bully dog tune. go to the 120 and fuel economy drops quickly.