I never installed GSX2 64bit so I didn't change anything but LiveUpdate only. Liveupdate takes care for my both sim FSX and P3Dv4.5
I think there's a lot of confusion here. GSX has two installers:
- The 32 bit installer CANNOT be installed in P3D 4 or 5, not even by mistake. The installer will simply see only FSX or P3D 1, 2 or 3
- The 64 bit installer installs ONLY in P3D 4 or 5, you cannot install it in FSX, not even by mistake.
However, even with the 64 bit installer, at least until last September, the GSX support was an hybrid application, because it was made by a combination of the Addon Manager, which is a native 64 app compiled with the P3D 4 SDK, and the Couatl scripting engine, which is a 32 bit app, compiled with the FSX SDK, which connected to P3D in backward compatibility mode.
This until last September. With that update, we released a 64 bit version of the Couatl engine, compiled with the P3D4 SDK, and it's installed automatically by the FSDT Live Update so, unless you manually configured P3D4 to use the 32 bit version ( still possible ), if you kept the program updated, you ARE already running GSX entirely in 64 bit.
So, I'm now not fully sure what you are asking or what your issue is. If you installed GSX both in P3D and FSX, and you ran the FSDT Live Update recently, everything is as it's supposed to be. If you are missing GSX from FSX, just install the 32 bit installer, so it will be added to FSX.