The MAAM DC-3 (actually an R4D-6) was first modeled for FS2000, upgraded for FS2002 and then extensively reworked and made payware for FS2004. It has since been further ported over to FSX. It is a really nice model, but is a bit dated. While still offered for sale, it has limited technical support.
Manfred Jahn's C-47 v3.14 is Native FSX and works fine in P3D v4. It is a worthy successor to the MAAM R4D-6, and is freeware.
Try it, it's here in the SOH Library, as well as about everywhere else. There are even two very nice MAAM R4D-6 repaints available for Manfred's C-47 v3. It is also very well supported as a current ongoing project! I have all versions of the MAAM R4D-6 and also fly Manfred's C-47.
That aside, I also would appreciate an FSX version of the Sikorsky HH-52A.