Welcome to the site. I will chip in that I think the balance of what's most important depends on the car, but certainly for a truck (as far as physical mods go) I think aeromodding would give you the most bang for your buck.
I actually just downgraded the engine power on my car (in hopes of greater fuel economy). Sure, I can't accelerate as fast, but I can still go down the highway as fast as I need to with quite a bit extra power if I feel like downshifting,
Again, welcome. Would be interesting to see some crazy aeromods on the truck.