Only the starting system is 24v on the CUCV Chevrolet trucks. The wiring harness on these is special because of the compatibility with the military trailer harness plug where all circuits are separate for tail, stop, left, right, blackout etc.
Here is another cheap solution I found on Steelsoldiers:
Or you can buy a cheap flat 4, and a complete 3-pin weatherpack connector (1 male end, 1 female end) and build your own adapter that will plug in right where the military trailer plug connects to the wiring harness. You can switch between military and civilian wiring in about 30 seconds.
http://www.steelsoldiers.com/showthr...l=1#post932493