I have seen the wedge type fender mount signals on a few GTXs. There was a 69 GTX in a collection out west that was in a few of the magazines some time ago. It was supposed to be an original car and had the wedge type. I know the Sport Sats had them in 69. I am using fenders off a sport sat and my body guy forgot to weld up the holes. I didn't catch it until the car was painted so I am installed the wedge type. But I have never seen them on a Road Runner in 69 (original anyways). But have seen them on some original GTXs.