I ordered a 12v wiring harness from Chevy Duty, it came numbered and color coded and simple enough to do in one day.
Do you want to change your truck to 12v or keep it original? They have 6v harnesses with heavier wire, so test the generator and regulator before you commit to all new hardware.
Here's what I ended up with:
90-amp internally regulated alternator
12v Interstate battery
12 to 6 voltage drop resistor, coil
12 to 6 voltage drop resistor, fuel gauge
12v halogen headlights
12v bulbs for tail, marker, dome and dash lights
12v cigarette lighter
12v heater fan
12v wiper motor
(am I forgetting anything?)
You're going to need wire cutters/strippers and a pile of connectors (I used crimp sleeves in some places, spade connectors in others). You may or may not need a side-terminal style starter switch, I didn't use one and it works fine.
On the downside, my fuel gauge reads high because I'm still using a 6v sending unit. The benefits are I can put any modern equipment in the truck (stereo, power seats, electric wipers, etc) and stuff like cell phones and laptops plug in to the dash.
Make a list of electrical components that need to be replaced; it may affect your decision.
Edit: I forgot the fuseblock I added for all the new stuff. :p
