72 -76 the fill pipe goes through from the outside and the screws hold the pipe to the quarter panel. On 67 -71 the pipe flange is on the inside of the quarter panel and the screws hold the quarter panel to the pipe.
Another words the 72 and newer fill pipe on a 71 and earlier car there will be no threads for the screws. The screws will just push right through.
67-70 are not vented caps and the tank is vented through the fill pipe vent tube. I always changed my 71's over to 70 duster fill pipe. The reason was for a positive vent for the tank because I run a 1/2 inch fuel line out of a narrowed factory tank.
Here is the problem They are harder to find then the 71's because it will have to be 70 duster only. Dart or Valiant will not fit. 4 screws verses 3 screws and a different bend that will cause quarter disfigure.
so that said your choices are
70 Duster only with cap,
71 Duster,Demon with cap
72-73 Duster Demon Dart Sport with cap but will have to use nuts on the screws and the cap will not fit correct turn or height
74-76 Duster , Dart Sport with cap but will have to use nuts on the screws and the cap will not fit correct turn or height.
I have several and save 70 and 71. I sold many on this site and do not have a count on what is still here or I would offer you a tube and cap. I know I have 71's but none I am willing to sell at this time. I was getting $125.00 for pipe and cap. High price but they sold instantly at that time.
Keep looking for a 71 they pop up. 70 California Duster is the same
