74 Dart won't start - ignition switch - maybe starter relay?

Seat belt interlock movie and booklet here:
MyMopar - Mopar Forums & Information - Browse MTSC by Model Year - 1974
Page 1 has the explanations and note that it says the circuits are entirely different than the warning buzzer system.
Page 8 explains the overide switch

low_kota said

I tried grounding the neutral safety switch with no luck. I get 0 volts at the starter relay, so the NSS checks out.

Click to expand...

Not quite, especially with the 74. Not quite as in, yes you eliminated the NSS as the cause. No in that you can't conclude its OK by checking the voltage at the relay.

To check the NSS, remove the connector from the NSS switch. With the selector in P or N, measure continuity (or resistance) between the exposed NSS prong and the transmission casing. IIRC its the middle prong but check on that.