[Flathead Fever]

I was a fleet mechanic for 30-years. Like others have said check the available voltage at the battery both with it "not cranking" and while it's cranking. If it's okay the next thing is your voltage is dropping too much at the coil. You want to check the voltage at the distributor with the primary wire to the coil "disconnected". Unless you know that the points are "both open", it easier to just disconnect the wire and check the voltage. When the points are opening and closing you will get the average voltage, not the available voltage to the coil, it's just easier to disconnect the wire and then check the voltage. You should have close to the battery voltage here when you "have bypassed" the resistor. You might have other problems too, but I would start with that.