The Trail Duster that I have been looking to purchase for the last 20 years is a 74 early model.
The early 74 models had the tops of the doors attached to the removable roof. The doors themselves were convertible doors.
Very very very difficult model to find. Only a half year offering. Late 74 models have the standard full frame doors.
I've had lots of ramchargers and a few trail dusters. Not once have I had a chance to buy the convertible top 74.5 version.