The dually trucks come standard with 4.10 gears.
Guages (EGT, Boost, Trans temp)
Call Jody at DP-Tuner and have him set up some tunes for you. Get a exhaust brake tune (Uses the Exhaust back pressure valve like a brake)
AIS intake is by far the best solution until you go high HP
Adrenaline HPOP give you plenty of HP oil and makes a huge difference in the 7.3
Ported housing for the turbo (Strictly Diesel) this cures surging.
Carry a spare CPS (Black one if you can find it) and a 10mm wrench.
Keep the RPMs up when climbing a hill and have fun..