Thanks for the update.
Points work fine and with a big block its not that hard to access the distributor.
If you're drag racing, a dual point is an advantage in the upper rpms. Not sure there's much advantage otherwise, even at highway speeds.
Checking the '68 Plymouth shop manual -
all engines used the same ballast resistor, should be 0.5 to 0.6 ohms (part # 2095501).
Two different coils were used.
With automatic transmission, primary resistance should be 1.65 to 1.79 ohms
With manual transmission, primary resistance should be 1.41 to 1.55 ohms
If using a coil with lower resistance, then the higher resistance ballast mentioned earlier in the thread is probably OK.
But if using coils with the resistance in the 1.5 to 1.7 ohm range, try to find a ballast resistor with the recomended .5 to .6 ohms.