Umberto, What P3Dv4 aircraft are available to use the KSDF D2-D12 cargo stands. It seem very difficult to find any cargo aircraft with a Left Front open cargo door that will talk to FSDT.
There's no need for the airplane to "talk" with GSX, you only need to have a proper GSX profile for it, which is easy enough to do. Of course, the first and foremost requirement to have an airplane working on Cargo Stands, is it MUST have a Main Cargo door on the FRONT Left, but I guess that's the same requirement as in real life, a 747-F or a 777-F, with the main Cargo door on the Aft can't use Cargo Stands, I think UPS park their 747s in the South apron area, numbered 9 and 11 on the charts.
The KSDF manual has some suggestions which planes to use: 757F, 767F, 727F, the MD-11F and the Airbus A300.
I think Captain Sim has 727, 757 and 767, but there are alternative, the manual has a screenshot at Page 7, showing the freeware 767-F from Sky-Spirit, GSX comes with a default profile for it so, as long as you have the correct model, there wouldn't be anything to do, it will just work. GSX also has another profile included, which is the freeware A300F from Tomash Ruth.
In order for the GSX profiles to recognize them, their main folder names should be as follows:
"TOM_A300-600F"
"AIRBUS A300F UPS" ( either of these two, the first is the base model, the 2nd is the UPS repaint )
"SKY SPIRIT2010 BOEING 767-323(ER) UPS FSX"