The second type of NCDH is easily distinguished by it’s different underframe, and that they all have flat panels the whole length of the wagon. The origins of this wagon appear to be NOGF and NOGX (HGM/HGX) wagons based on information on the comrails website. It also mentions NOAF (BD) wagons, but I believe these to have been recoded NDNF (see separate blog entry).

If indeed the origins are NOGF/NOGX wagons, Silvermaz (Casula Hobbies) have a model of the HGM/HGX wagons available that could probably be kitbashed.