Non-AC Heater Box or Heater Box Cover for 74 Duster

Well, careful as I tried to be, I somehow managed to crack the cover of the heater box on my 1974 non-AC Duster. I thought I had the J-jook disengaged from the fresh air vent but it looks like it snagged on something when I was dropping the heater box. I only need the heater box cover (the part with the fresh air door and J-hook), but will take a complete heater box if necessary. Send me a PM if you can help.