Back in the day they had the dash lights in with the tail lights so if your dash lights were out you usually knew that your tail lights were out , that was just a way to know but i would just replace all the fuses anyway if they are old it never hurts and they are cheap versus a ticket but if there is a fuse for the dash lights chances are it is bad but also there might be a inline fuse , still if nothing i would just do the old trick and plant a wire on the neg; side of batt; and run it to your tail light bulb and put it in between the side of the bulb and the casing and you will have a good ground ( just one way to rule out grounding ) hope it will help you but my guess is its a fuse