What exactly do you mean by the "dash"? Here is what I know....
The metal frame is the same on the "Dart/Demon/Duster/valiant from 1970 to 1976 with the exception of the 1970 340 model.
The dash PAD is the same from 1969-1976.
The guage cluster physically fits from 70-76 but there were changes. I believe in 73 or 74 there was an seat belt warning light. A year later an EGR light was integrated. The early ones had a 120 mph speedo, the later ones went to 100.
The heater controls changed in 1973. The panels and linkage was redesigned. The glove box doors physically fit from 67-76. The later years had a plastic glove box insert, early cars were cardboard.
