What 727 is this?

According to my list it's from a 69 D-100 pickup with a 383 engine. Why are you specifically wanting an A-body transmission? The only difference with a 727 from an a-body and a truck is the truck trans might hold more clutch plates and have 4 pinion planetaries (all good things IMO) where-as the a-body trans probably has 3 pinion planetaries and holds less clutch plates. If your Dart uses the stock console shifter the truck transmission may not have the 2 lobes on the bottom of the tailshaft housing to mount the plate that the shifter rod goes through but that can easily be remedied by swapping the housing to one that has those lobes.