"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."

I have a copy of the build sheet from a St Louis built GTX I owned years ago. It was a 440-4 car with the N97 package. N97 is called out on the build sheet and the N42 slot is blank. I had always thought that the tips had been deleted when the car was ordered. But I realize now that it was tip delete due to the N97 choice.