That's from the 60/66 series but not exactly sure which years it fits. Some of those years did not use the mounting frame as you have, they used a track. I also believe that the GMC and Chevrolet were different depending on year. I have a set without the mounting frame and was told it was not for the 1960/61 Chevrolet. I am hoping this question gets resolved and archived, it's a common question. Maybe RJ or COLLETESBRO can answer this.