N97 was a no-cost option that was required for 440+6 4spd cars delivered to California. N42 was included in the GTX package and did not need to be checked off on the order form. N97 440+6 cars did get N42 tips. Since this was a standard feature (an option for road runners), there is no box on the order form to delete the tips. Optioning the N97 code on a 440 4bbl car did eliminate the N42 tips from all the fender tags I have seen. I have not seen an original N97 440 4bbl car (with original exhaust) to confirm this.