73 Duster only starts in "run" not start posistion

Somebody else (you?) had this same problem a few weeks ago. Sounds like a problem in the "ign start" wiring (usually brown 14 awg). I think the manual calls that IGN2 on the key switch.

Disconnect the coil+ wire(s) and disconnect the yellow wire on your starter relay (so starter won't turn). Measure the resistance from BATT+ to the disconnected coil+ wire, with the key held in the start position. Should be < 1 ohm. If more, start tracing back from coil+ to:

ballast downstream side (brn wire)
bulkhead engine side (brn wire)
bulkhead cabin side (brn wire)
ign switch (IGN2)
ign switch feed (red?)

Continue until you find the main resistance. My money in on the bulkhead connector, but your new ign switch could be bad. Clean all terminals as you go with a file and spray contact cleaner, and coat with di-electric grease. You need a wiring diagram, and can find in FABO w/ a search.