Car won't even crank...

My 74 Duster still has a starting issue...
I will turn the key and the car WILL NOT CRANK.
It will fire right up one day and not the next.
A little help here?

New parts...
Voltage regulator
starter
battery
neutral safety switch
starter relay
key switch
resistor
electronic ignition
Coil
All 74 seatbelt lock have been removed or disconnected.
Ive gone thru all the wiring too.
All grounds are good.
Please help....

What have you done or checked since we last talked?

Do we understand that it will not crank if you jumper across the starter relay?

Have you / can you jumper across directly at the starter?

By the way, where are you located?