Mike, FWIW, here are a couple photos of the OE accessory Guide traffic light viewer in my '53 Bel Air. Mounting in a truck will be somewhat different, I expect, but with the cars, the mount uses an existing windshield trim screw. That scheme mounts the base as close to the windshield as possible. It is mounted roughly centered on the steering wheel. Hope that gives some ideas for your mounting.
NOS Guide accessory units pop up on eBay periodically. I prefer the type in my Bel Air that has a Fresnel lens, which picks up the illumination from the traffic light quite well. Having said that, I don't have experience using one with a visor.
