Heater Core replacement help

[Bigru]

I'm in need of some help, I have a 65 SWB with factory air and I'm trying to replace the heater core, blower motor and evaporator. I started by removing the screws on the top of the heater core, then I realize I couldn't get the core out that way. Do I need to drop the factory ac unit in the cab to remove the heater core and blower box in the engine bay? Does anyone have any pics or a video of this removal process? Thanks for the help!