You will find that a lot of things were thought of a long time ago. Auto dimming headlights? Cadillac did it in the '50's. Headlights that turn with the wheels? That was done the first time in the '30's by Tatra. First auto on/off headlights? Cadillac in the '60's...
My point here is that just because it's old don't think it doesn't have something as a feature or that it wasn't thought of back then. Dimmer switches have been around a day or two, as have other things. Get to know your truck intimately, that's all I'm saying in a wordy round-about way
