I was always told it was 10 years too, but everything is up to interpretation. I wrecked my 69 Dart GTS in 1978 and they just laughed at me. I did get inner fenderwells from the dealer that were later model. I know that the NOS fenders for Darts were not even close to original, recessed antenna hole, different inner fender mounting, different in the front near the hood adjuster, so not all NOS parts work good.