I would map things out before you install it. Here is the basics, you can make a "truth table"
POWER IN. This was originally a large gauge wire, varied in color.
ACC out. This connects to POWER in both ACC and "RUN"
IGN1 "run"..This connects to POWER in "RUN" I would guess also shows continuity to ACC in "RUN" IGN1 is hot ONLY in run, and goes dead in START
IGN2 and START. These are separate contacts and should not show continuity to each other in "OFF" or "RUN" or "ACC" Both these should connect to POWER when twisted to "START" IGN2 feeds power to ignition system in "START" and it's purpose was to provide "full battery" power to ignition and to bypass the ballast resistor in START
START was yellow for most years, IGN2 was brown.
The START wire only went one place as well--out through the bulkhead, to the starter relay
Since you have a 74, make sure the yellow wires at the seat belt relay interlock/ reset--out on the fender apron under the hood--make sure that you splice the two yellows permanently together to disable that interlock. Also don't forget that start relay will not engage without a ground at the second terminal of the relay coil.......the transmission neutral switch with auto, or the clutch switch with a stick
