Turning key is a crap shoot

Go easy on me....I do have a meter and also a set of reproduction shop manuals. I was just looking for a hint or two....hahaha. Electrical is definitely not a strong suit of mine. It seems odd that for the few times I turn the key and get nothing then it turns over so why a connection problem and then no problem? The interior except for a beat up bench seat and Hurst shifter is gutted. How would I know if I have interlocking seat belts?

dude , see the picture I posted ? ground that terminal to the body. if it starts every time you have a ground problem, theres your hint. there is a clutch safety switch connector there now, which provides a ground connection when the clutch is pushed in. follow the wire inside the car and you will see the switch mounted behind the clutch pedal. the switch is probably going bad. you want a quick fix , I just showed it to you. just remember it will start without the clutch being pushed in now. the starter relay case MUST be grounded to the body. clean all that up. your 72 does not have a seatbelt interlock