I have a newly rebuilt 429. Everything on the engine is new, starter, solenoid, battery ect. It started fine over the winter, now I get a clicking sound from a "switch / relay" mounted on the firewall and the starter will not work. Any ideas how to troubleshoot this?

Sounds like a solenoid problem,to check it just run a jumper

I check the starter and it is good. I replaced the "Starter Relay" still will not start. Anyone familiar with the "Starter Relay"? Three wires go to the "Relay" One is constant hot, one is the ignition wire and one completes the circuit. I am assuming. When I turn the key on, the Ignition wire is hot, When I turn the key to the start position the ignition wire goes dead. I would think it would work opposite of that. A problem with the Neutral Safety switch? The Ignition Key?

could be a bad ground. Check all connections for clean and tight

i had same problem on mine, found out fusiable link on starter wire was shorting out, hadn't blown the link.

Thanks for the input. It was the Ignition Switch mounted on the steering column.