Determining letter ruling applicability

​​​​​​​We are a dealership that sells a certain body type. A customer gave me a copy of another dealership’s letter ruling in which the Internal Revenue Service determined the bodies sold by the other dealership were not subject to FET under Section 4051. Those bodies are substantially similar to the ones we sell, and we typically charge FET on our bodies. Does this letter ruling mean we can stop charging FET?