I’m not sure about that 64, ask an ai about 409 and it will tell you all about household cleaners. That’s a neat manifold James. I had one that on a 327 a long time ago. The Rochester 4 jet even worked good, probably because I never took it apart. Ha. Hey 64, I figured you would dig the intake on the 55. I think this might be an early m/t because it doesn have any bosses for linkage and the right carb flange is machined lower than the left. I just stuck a few spacers under the low one. This thing won’t let me post a clear picture