What are the differences between 65-66 and 67-73 Factory A/C

convx4 said
So, Am I looking for under dash parts from a 66-72 factory A/C car, Or 65-66 car?

The 65/66 underdash parts are the same other than the actual bezels. I don't know if 67-72 is the same or even similar as I don't have anything to compare to the 65/66.

convx said
I thought the the 65-66 Factory A/C cars used a 4 push button dash controller, while the 67-up used a 5 push button dash controller.

I parted out a 65 Dart GT with factory air, a 66 Dart GT with factory air and pulled all the AC stuff from a 66 Barracuda in a local pic 'n' pull and all used the 5 push button controller. Got a couple of 65 Valiant/Barracuda heater/AC bezels and they're 5 button also. You might be thinking of the 65 and earlier B Bodies which did use the 4 button controller.

convx said
I have a 70 dart with factory A/C that I can use for a reference. This is my first early a-body.

If you'd like I can make a paper template of a 65/66 firewall with all the pertinent holes needed to convert to factory AC so you can compare it to your 70.