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

Thanks for all the replies!

I tried grounding the the terminal for the NSS on the starter relay, and nothing.

I have 0V at the coil in start and run

I also had a spare ballast resistor and swapped that out with no luck.

The car doesn't have seatbelts in it, and has started several times without them, so I think the seatbelt interlock has already been bypassed.

I'm not sure if this would matter, but after the engine install it would start and run fine. The only thing I changed before it started acting up was install the alternator.