"I have had this happen in my 70 Charger. I have a MP electronic conversion kit in it with a Chrome box. it was an intermittent problem that never left me stranded but still tested my patience at random times. Once every few months, it would crank and crank but not start. I'd check connections everywhere, jiggle things, cuss and complain, THEN it would just start like normal. Occasionally I tried spraying ether down the throat even though it was getting gas. It worked half the time, I don't know why.
For the heck of it, I tried another distributor. The replacement had a smog engine curve to it...I was just looking to use it to test. It started reliably every time. I figured that I'd just fix my MP/Mallory distributor, so I replaced the magnetic pickup in it and properly set the air gap. That was 2013. It has NOT failed to start since then."

No money is needed, just applause.