Certainly.
The initial post was asking about aftermarket HVAC, and having recently done that I threw in my two cents.
Vital to this discussion is alternate approaches such as the one Dennis used and what Julian just now proposed.
I would not have gone to the effort required if I wasn’t already starting with a bare shell after the collision repairs were finished.
An aftermarket HVAC offers more flexibility in how it is controlled where as upgrades will retain the same basic control system. One thing easily done is upgrading to a more modern three speed motor and you can also find DC motor potentiometer controls available on eBay so your blower fan is fully variable
Larry