First up, tail lights. Due to the license plate light, at least the lower right bulb must be white light. Due to the weird inclination of the bulbs, any solution must avoid being too directional. Lastly, the more lumens, the better. The best option I could find were these LED bulbs straight outta China:
Another option is to paint the inside of the housing gloss white then put a #81 bulb in the bottom socket for the tail light (6cp as opposed to the OEM #63 3cp). Then put a slight bend in the bracket between the sockets to allow a #1129 21cp bulb to clear the housing and lens (as opposed to the OEM #81) for the brake light.
My 6v '38 tail light on the left compared to my modern 12v truck on the right. You are right about the plastic lens passing more light than the glass.
