Hi Avers! From what I understand, there's a few mods you can use. Which one depends on what Super Mod you're using.
For stock SH3 and GWX 3.0:
WideScreen GUI for GWX3.0&StockSh3
This is the one I use, and it works with GWX 3.0:
Conus' SH3GWX Widescreen Mod
and lastly one that works with NYGM:
WideScreen 1920x1080 Project
I can only speak for Conus' Widescreen Mod, but it works great. Note that these will ONLY work at 1360x768 resolution. With some Antialiasing enabled through your video driver it should look pretty good.
I also need to mention I needed to run SH3.exe in compatibility mode with Windows XP Service Pack 3 for the widescreen mod to work. This was with my Windows 8.1 system.
Good luck!