68 fenders won't work on a 69 because the headlight is mounted lower and further forward on a 68. One could change over the entire front headlight panel portion to modify it though and also change the side marker.
69 fenders are the hardest Dart fenders to find
68 fenders won't work on a 69 without serious reworking. The 69 fenders have the headlight mounted higher and further back than the 68 fenders do. So besides the obvious side marker difference, the headlight mount panel is totally different. You could drill the spotwelds and change over the entire front panels to make the changes