73 Duster Electrical Issue

OK the starter relay functional path (for the relay coil) is from the key, through the bulkhead, to one of the two flag "push on" terminals, through the coil, out another wire on the second flag terminal, and down to the center terminal on the neutral switch. THAT TERMINAL on the NSS should be ground when the trans is in park or neutral. To eliminate that, remove that wire, and ground the terminal on the relay from which you removed it. That will ground the start relay coil and eliminate the NSS.

Next, twist the key to "start" and see if it cranks. If not, monitor the other relay coil (flag). You should have voltage there in "start"

If you DO have voltage, and it won't crank, you likely have a bad starter relay