Heater Box, AC/Non-AC

My '65 wagon originally came with air conditioning, but all those parts have been removed except for the heater/AC box. I drive the car when it's cool outside (usually 30* and above) and it has pretty weak heat (thermostat is fine). I've read that the firewall between the air and non-air cars was different; can anybody verify that?

I'd like to someday swap in a non-air box and control panel to avoid some of the needless complexity of the current system and all its related vacuum lines. Is that feasible or am I out of luck?

Does anybody make rebuild parts for the AC heater boxes?