you can contact Stant Manufacturing.. they produce radiator caps, locking or un-locking gas caps. Several years ago, I measured the diameter of the filler neck at the gas cap for the in-cab stock gas tank and also for the 2 under bed tanks.... Stant replied with the part numbers and the 3 caps were available all keyed alike !.... Take this info to most any auot parts dealer and they can order for you........Jim
www.stant.com