Heater delete air boxes? Seen em?

Hi all, I'm going to remove the heater from my 75 duster and wondered if theres a heater delete air box to fill the hole left by the heater in the cowl? I have a right side one from a New Zealand valiant, but its not quite the same as the left one on my duster. I have the radio and heater delete plates from NZ valiants for the dash, but wondered what the US cars used? What did hemi darts have? Any pictures?