I have a ' 72 and have dealt with the dead engine deal on previous occasions. A frequent culprit is the starter switch itself. There is a little wishbone shaped piece in there which sends power to the coil and to the starter. This contact becomes worn and sometimes sends power to the coil and sometimes doesn't . With mine I just had to jiggle the key in the ignition in the running position and it would run and not, run and not. If you
always have power at the coil, the next place to check is at the points. Is the rotor consistently picking up power and sending it to the plugs? When you still have power at the coil have you tested for spark at the plugs? Stick a screwdriver into the plug boot and hold the shaft of the screwdriver near a good ground. You should see spark there. Be sure that your problem is electrical and not intermittent fuel supply with a hung up carb float. Can't help you with the voltage regulator - this is still a mystery to me but I do know that problems with them are relatively rare. Keep us posted with the results of the above tests.
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.