In desparate need of early model 71 dart fuel cap

Factory caps were body color. Service replacement caps could be had in primer (for bodywork jobs) or in chrome with chrome handle (for "I lost my gas cap but I'm not going to pay for paintwork" situations). Aftermarket caps often had black plastic handles. See here for complete info on the fuel tank vent system on your '70 California car. Removing it is kinda pointless.