A/C Heater Box Modification?

This is probably a really stupid question, but I'm wondering if an AC heater box can be used for just a heater/defroster.

I pulled the heater box this weekend in my 68 Dart AC car thinking I'd get rid of it and patch the holes on the firewall. At first, I was going to cut the vent side off and modify it so I'd at least have a fresh air vent. Now that its out, I'm wondering if I could keep it pinned in heater mode and get rid of the A/C garbage that wouldn't be needed (evaporator, associated doors, etc).

Has anyone done this?