At lot of our 40-50 year old cars have developed so much internal resistance in the wiring, that probably plenty of them can run without the ballast resistor by now.
I know my Dart had, until I starting noticing the voltage losses at connectors and old wiring.

If you want to 'check' if your coil will live without using a ballast resistor, try to feel how hot it is after a short drive.
If it's way to hot to the touch, it probably won't last very long.
Better use an infrared lasergun.