I tend to agree as these cars need a good strong spark to keep going, I do not think they will run with a weak battery, a little stronger battery and they will run until that little extra power is eaten up by the lights being turned on. When the alternator quits it runs on battery power until that gets too weak. That is why you cannot bump start a six speed with out a good battery, maybe you cannot bump start them at all, I do not know.
That is what I have learnt, I hope I am correct.