Where is the back up light switch located on a 1979 Ford F250 Custom?

My husband just recently bought a 1979 Ford F250 Custom and is having trouble finding the location of the back up light switch. We've googled but have not turned up anything. A few of his friends gave suggestions. If anyone could shed some light as to where it might be it would be much appreciated.Where is the back up light switch located on a 1979 Ford F250 Custom?It would be on the tranny at a location where the shift linkage could contact it when moved to reverse.Where is the back up light switch located on a 1979 Ford F250 Custom?Might be at the bottom of the steering column inside the truck, if not, at the transmission shift lever