starter relay

There is a way to bypass the solenoid to see if it is bad; can't tell you how since I never had to do it on either of my foxes, and I don't think the solenoid on my '65 is the same.

sounds like you simply dont have the needed amps to start it. try hookin a jumper battery (like jumping the car) and see if it starts. you can have plenty of volts, but not nearly enough amps to start it (often there is a surface charge, but nothing behind it).

to bypass the solenoid, put a screwdriver across the big lugs on the solenoid. make sure you are in neutral, etc.
if it starts (i dont think it will), then second test:
take the push on connector off its stud and touch it to the lug with all the cables attached to it (the other lug only had the starter cable on it). if it starts this way too, the solenoid is good. if this also passes, then problem is likely in the clutch safety switch/neutral safety switch or the ignition and wiring.
good luck.