1966 Skylark Heater Core Replacement

I am trying to determine how to replace/access the heater core on my 1966 Skylark which is equiped with an AC.

Did you (or anyone else) figure it out? I too am working on a heater core in a 1967 Skylark with air con. From the inside I am able to get down to a metal cage housing the heater core by removing ducts and glove box and more duct work. It is like the whole car was built around the freakin heater core. So I am to the point where I can see and move the core but it's still in this metal box thing. Do I need to take off the AC Box under the hood?? :nono: