I'm in the process of painting my wall of fire and making it more beautiful. I drive a 1964 Cutlass that came with air conditioning. I would like to replace this air conditioning box with a normal box for the blower. Does anyone have experience with the master kit from AC delete like here attached. Is it absolutely necessary to use this box or can I do the conversion with a normal blower box

https://www.acdelete.com/pages/64-7_A-Body.htm

 

The A/C firewall has larger cutouts than the non-A/C firewall, which is why you can't simply replace the A/C box with a heater-only box unless you also replace the entire firewall or at least weld patches into the holes. That aftermarket A/C delete still uses the original vacuum-operated A/C box under the dash, which means that you also have to retain the A/C control head and vacuum system. It's not a clean installation. Of course, your A/C car also has the cutouts in the dash panel for the round ducts on the ends, which heater-only cars do not have. Your call on how much work you want to put into this.