engine/gauge wiring question

[1972BackInBlackC10]

i have done some research on this but need to double check on some things im not sure about or couldnt find info on.

i want to upgrade my dummy light cluster to a full factory gauge cluster oil,temp,amp, from what i understand all the wires for the swap are in the harness and just need to be relocated on the clip for the cluster correct? there was something about running a wire from the red wire on the alternator that im not sure where that wire goes to

second, are all the wires on the engine harness there for this cluster swap or do i need to get an engine wiring harness from a truck that had the full gauge package? any info on this or something i missed would be appreciated

thanks
mike