How to remove Heater Box in 68' Dart WITH factory Air

We have the dash out, an a 69 Charger, next week the heater core has to come out. With the room to look at it (we have never done this); we have loosened 4 nuts firewall- engine bay side. It is loose. But there is linkage, and the accuator is part of it.But easier to see with dash out, sounds like 68; will take pics, and post here.