Car won't even crank...

My 1974 plymouth duster has had an on going issue of when I turn the key absolutly nothing will happen.
It tends to act up when it's warm out for example if I stop for gas, when I'm done and ready to fire it back up nothing will happen. I will turn the key and the car WILL NOT CRANK. It just happens randomly too... will fire right up one day and not the next.
New parts...
Voltage regulator
starter
battery
neutral safety switch
starter relay
key switch
resistor
electronic ignition
All 74 seatbelt lock have been removed or disconnected.
Ive gone thru all the wiring too.
Please help....