IMO, there are 3 stages of engine mods for the 3.0.
Stage 1: ( Simple bolt-ons, fairly inexpensive, will improve throttle response, slight increases in power, and can improve mileage)
underdrive pulleys
a decent cat-back exhaust
electric fan
Air intake kit
*an sct X-cal tuner
Stage 2: (More indepth install requirements, increased cost, work best in conjunction with Stage 1 mods)
porting/polishing heads and intakes
roller rockers
headers
*an sct X-cal tuner
Stage 3 : (Most advanced, will see largest power gains, highest cost, )
Tom Morana products
Forced induction
*an sct X-cal tuner
*I realize that you already have a superchips. I'm recommending an SCT x-cal because I've heard from several 3.0 owners who have had both the superchips and the x-cal that the SCT has tons more capability. (if you don't want to spend the money on another tuner, you may be able to find someone to write custom tunes for your truck that will allow you to utilize the Superchips tuner. Either way you go, wait til you're done modding.) The tuner can be done at any stage, but making the tuner the last mod you do will allow the tunes to account for other mods, and therefore have a larger net affect on performance. It also keeps you from spending money on additional tunes if you mod things after purchasing the tuner.
Thats strictly engine mods. Reducing the weight of your truck, and changing the shift points if your truck's an auto would help (another advantage of the SCT x-cal). If you've got a stick, then consider a short throw shifter from Hurst. Traction is key as well, so decent tires, and a limited slip differential, or full locker will do wonders.