If I am to understand previous statements ,the DOAZ cap is supposed to fit a regular 69/70 Shelby filler neck because it is a service replacement. The DOAZ cap like what Marcus has in his article will not fit the regular Mustang /Shelby filler neck. Maybe Marcus had one misboxed but it is doubtful. It has too tall of a neck as mentioned in the article on the backside compared to a regular vented cap on a 69/70 Shelby. I had one recently new in the box that I sold to West Coast Cougars because it would not fit any regular filler neck 69/70 Shelby.I have had a couple of them that I had purchased because the MPC number was has it supposed to be a regular replacement for 69/70 Shelby. I have a hard time believing I was so unlucky to have all three mis boxed because even though the MPC calls out for it as a replacement it will not fit. All I can say is that to pre test it on a regular filler neck before purchasing otherwise you may have a unpleasant surprise.