I would think you would use the DSM harness, and just hook up the one wire from the ignition switch to the starter solenoid. Someone please correct me if I'm wrong.
The sub harness should connect to the battery and the alternator. They are all power wires and shouldn't connect to anything else as far as I remember. The only wire that goes somewhere else is the starter solenoid and should be black w/ yellow. I think it even has a connector on it.
Do it in a Datsun!
1972 Datsun 510
7-bolt 4G63T, EVO 9 pistons and rods, Garrett GT3076R, "flipped" stock intake, Toyota R154, Z31 R200 w/ CVs
if you can't find a 1g dsm starter harness, you could just make your own starter harness.
you find the four pin connector on the transmission branch, it has four wires running through it, two of them are red (these control the backup lights)
the other two wires are thick black with a yellow stripe running along the side. the two black/yellow ones are what you need they both merge into one wire before they connect to a single blade switch on the back of the starter.
the other ring terminal on the starter goes to the positive + battery terminal.