Help me ID this Fuel Filler Neck...

You have a 1971 Duster Demon tube. One year only except california 70. yours is a three screw , mounted from the inside with no small vent tube. uses 71 cap only

A three screw mounted on inside is with small vent tube is 70 duster only. uses 67-70 cap

All Darts and Scamps have 4 screws