Lever is the tranny kick down, there should be a rod connecting it to the carb. Rod connection kicks the tranny into a lower gear when you mash on the gas. If NSS is out of adjustment, you might also have problems starting the vehicle unless you monkey with the shifter. NSS might still be bad for just the reverse lights, any adjustment you make to the switch will affect whether it you will be able to start the truck in park or neutral. I would guess and say that you need a new NSS.