I'm putting a stock left side taillight on the right side of my '46 1/2 ton so i'll have two. I'll wire them with dual elemement bulbs so they'll work as taillights, break lights, and turn signals.
I'm pretty sure I could coast on the single tail light due to the trucks age, but i'm doing it simply for saftey reasons.. and i've seriously considered installing one of those "third" brake light LED deals in the back of the cab just above the rear window.
As i'll be using the truck as a daily driver, I want to make absolutely sure when tooling down a county road at night that the clown behind me doing 75MPH knows theres a rickety old truck in front of him doing 50MPH.
I'll be upgrading the electrical to 12V, and putting some halogen headlights in. I'll also put dual element bulbs in the front parking lights to act as parking lights and front turn signals.
That will give the truck the outward appearance of being generally stock, but be safer in this modern age of inconsiderate and often in a hurry drivers.
