you need: (listed from most important to least important)

Tachometer (preferably not Indiglo or 5" monstersized)
Speedometer (so you dnot break the law and have the Man on your back)
Boost guage
WB02/UEGO (all else are Narrow band and not accurate enough)
EGT
Oil pressure
COolant temp
Oil Temp
Fuel level
Cylinder head temp
Trans Temp
Brake pressure
Voltmeter
Barometer