When I had my race car, with battery in the rear, main battery cable went to the starter lug on the starter.
I then had 2 wires running up to the starter relay,
1. a #10 from the big starter post to the big stud on the starter relay (which also supplies the fusible link).
2. a #10 from the starter solenoid to the starter relay to energize the starter in start position.
Your #1 wire is bad or not connected.
That is if you are still using the fusible link at the starter relay, which sounds like you are.