Changed out engine in 75 with one from a 73. Brought no FI with it. Using carb. Am using the engine compartment harness from the 73. I can figure out what goes to what, I think. Black and Black/Purple ones to the + of coil. Green/white to oil pressure unit and starter conections for the rest, except the white one. The question is the White Wire that shows to be the #12 of the 12 wire engine connector. Following the control board map show the circit going to the #13 of the 14 wire connector. What does this wire go to??????

I believe the white wire goes to the supplementary air valve used in the FI system to get a higher idle at cold temperatures.

Yep, air valve wire.

73 only has one wire on the + side of the coil. Think it's just the black/purple.

You guys better look at a wiring diagram. The black wire goes to (+), the green wire and the black/purple wire go to the (-) side of the coil. Black/purple is the tach wire.

The Cap'n