Take a look at this
40 watt solar panel.
It's physical size will go well for attaching to a tool box lid in the pickup bed. Electrically, 40 watts will be plenty for any 12V accessories you may want to use.
Put a 12v battery in the tool box and connect to your solar panel and a two wire cable (I used a old extension cord). Run the two wires into your cab (keep it hidden so your truck looks OEM). I hooked my wires to the cigarette lighter on the dash and also have a radio hidden in the glove box that is connected. I have a volt meter with blue tooth and USB I plug into cigarette lighter so I can play the radio, charge devices, and monitor the voltage from the dash without opening the glove compartment. When I go to a show I can pull out the blue tooth/usb device out and put my cigarette lighter back in.... looks just like it did in 1946. The only problem I have run across in the three years I have used it, people ask if my truck is solar powered then I explain what the panel does.... no problem really. Battery may get low at night depending on your current draw. I haven't had a problem with that.
Note 6v led tail lights. I did add the right tail light which isn't OEM GMC in 1946.
