Difference between '72 & '73 Heater / AC Box?

[marianamaya]

Is there a difference between heater / ac boxes between 1972 & 1973 A bodies (Dart specifically). Several 1973 on ebay.

Can't I use any box from 1970-76?

 

[RedFish]

No. 72 and back or 73 and up.
Watch how the fan switch operates for a quick indicator. One switch moves left to right while the other moves up and down. Every little thing including those switches is different. Even the bigger things like firewall openings are different.