Anyone swap HVAC unit from donor?

Thanks for taking the time to comment! This is exactly what I want to do! I just found his build online, he did an incredible job! I can't find any dimensions of the Ram 1500 heater box online, I'm going to head to the junkyard and see if they have any pulled to check measurements to see if I can tuck into 64 Cuda area. Do you think the Dart and Cuda have similar space behind the dash? In photos it appears the Dart dashboard is a little larger in depth, but could be deceiving.

I don't have any experience with the early a-bodys. All my stuff has been 68 and newer. But just from pictures I've seen of early Cuda interiors, it does look like you probably have less room than the later A's