Gauges (at a minimum):
1. Fuel Pressure
2. Boost
3. Exhaust Gas Temp
4. transmission
Get some type of Air Filter Intake
1. AFE (do not buy a K&N)
Fuel system upgrade:
Look into doing something with upgrading the fuel system on the 24v trucks. The stock LP is of poor design and can barely supply enough fuel for a stock truck. There are many alternatives out there, but with this system, I would recomend a FASS-1. Some upgrade is an absolute necessity if you eventually plan on producing more HP.
Exhaust:
If you are handy, you can build a 5" exhaust for around $200 (no muffler), all you will need to buy is a 4" downpipe, 4-->5" coupler, 7' 5" tubing, 3* 5" 45deg, and 1* 5" 90deg elbow (and a tip if you like). Don't forget hangers (and clamps if you do not weld it together).
transmission:
Get some type of larger cooling system for your transmission. Heat destroys transmission components, anything over 200deg will start to bread down fluid and destroy the soft parts of the transmission. A larger pan and an additional aux cooler will help.
Doing this will not really get you any more power, but it will prepare your truck for more power. Better to go into Bombing prepared, then to break something first, then have to spend 3 times as much to get back to where you were.