Wiring Diagram for 72 c/10

[canadianchevy72]

I bought a 72 Chevy c/10 with an engine and tranny from an early 80's truck problem is most of the wiring wasnt done and some wires were wrecked. Ive managed to wire up the water temperature gauge and the tachometer and the oil pressure but I am having trouble with the voltage meter and the speedometer. First of all voltage where do I put a wire to test it? Just plug it in to the fuse box or by the alternator or what? The speedometer isnt hooked up there is one wire coming off the tranny it is orange and coming off the left hand side near the pan could this be for the speedo? It would plug in at the back of the speedometer correct? Thanks for the help and If anyone has a wiring diagram for a 1972 chevy truck Id appreciate it.