that's a cargo light pull knob might had been a option my 69 camper special has it although the knob itself was missing . I found the whole switch on e bay for 50 bucks I didn't care I bought it for the 50 bills the knob lights up red when you pull it out and behind the cab / cargo area light comes on . they sell a aftermarket look alike with a red plastic knob that lights up as well although the factory Ford one Good luck there no longer available.

I would go out into the rurals and look for someone who has a '67 - '72 junked F-100/150 sitting behind the barn. Might be a totally rusted out heap but as long as it still has the instrument cluster you may find some gauges that are still working and you will have original Ford gauges. And if you find one with all four gauges, that's a bonus and you wouldn't have to hang after- market gauges on the bottom of the dash panel like the one in this video.