[Kurt in NJ]

Measure the voltage at the bulbs, compare to battery voltage--- it won't matter what bulbs you have in the electricity is not getting there

A 6 volt car (Packard)that I work on came with every type bulb, all were dim, only 4.5 volts making it to the lights. kept tracing back and found the loss at the ammeter, it had rusty nuts, replaced them, now all lights bright