Dart heater box interchange

Mineallmine said
Looking to find out what year heater boxes will fit in the early A's. If I have figured right 63-66 dart are the same, but what about the later Darts? I saw a 1970 (I think...somewhere from 67-70 IIRC) for sale and it looked pretty much the same. The only obvious difference I could see is that 63-66 have heater ducts pointing down and 67 up have them pointing towards seat. Is there some other fitment issue? Does the duct facing forward matter? Mine has the usual broken door and this one looks good, so was considering the swap if it will work.

Thanks

I believe 63-66 non A/C are the same. I recently sold a 66 A/C box which is the first I have come across. I'm not an expert on 67-76. 75-76 non A/C and
A/C boxes may be different than 67-74. The firewalls and front floor hump are a little different on 75-76 cars because of catalytic converters.