I left the 1500 coils in mine, the dana 60 is a direct bolt in replacing the 44, When I swap the 60 in mine, I got everything from the steering box down, and it bolted in with no modifications. The track bar is the same part number between the 1500 and the 2500, so I left it on the 1500 (mainly because I did not have a puller).
The rear ends will not directly swap,
-the leaf perches on the 1500 are set out wider than the ones on the 2500, so they will need to be cut off and replaced with new perches.
-the speed sensor plug is a different, just swap the sensor out with the one in the donor vehicle.
As far as the frame goes, the frames were almost the same. The front cross member on the 1500 is just a single c channel where the one in the 2500 was more double channel(see the drawing). The transmission cross member was not as wide from front to back as the 2500. But the frame and the mounts are the same height, width, and thickness of material, until it gets behind the cab. Then the 2500 goes to 1/4" thick material compared to the 1500's 1/8".