Warning: You will need to have 3ds Max version 2016 or higher, GTA V and openIV installed prior to installation of GIMS. 
Make sure each other software works independently before attempting to install GIMS.

1. Copy _3dsmaxroot data to 3ds max root like 'C:\Program Files\Autodesk\3ds Max 2018\scripts\startup'
NOTE: DO NOT replace the whole startup folder, only add the GIMS files to the existing folder!

2. Copy _local to 'C:\Users\yourusername\AppData\Local'

Enjoy :)

Changes with v.2 (by Stochastic Hegemony):

- Faster import times;
- Faster export times;
- Can now export without all the textures present without hanging a long time. 

Note that the export command will still take a long time if you use a very complex scene. This version has function time tracking commented out.