GregTech 5 for Minecraft 1.7.2 and 1.7.10. Required Versions listed in each Release.
The Source Code in this Repository is just the latest API files from back then.
More Details on the Release Pages
https://github.com/GregTech6/GregTech5/releases/tag/v7.2.50315
https://github.com/GregTech6/GregTech5/releases/tag/v7.10.50707