Gama Aviation Gulfstream G550 N501GM for the HTAI model.
These are textures only.
The HTAI Gulfstream G-V model is required.
It can be found at http://htai-models.com/downloads.html
The converted P3Dv4 model can be found here:
https://www.alpha-india.net/forums/index.php?topic=26276
Flightplans available here: https://aibizjetproject.wordpress.com/tag/gama-aviation/