DOOMExtract is a command line operated file that can perform operations on the resources file for DOOM, including extracting it, and repacking mods into it. To install extract this to the "/base" directory and drag "gameresources.index" onto the program. This works in all current available builds of DOOM.

To install mods, run the install.bat or edit it to the mod install folder you wish to use.

This was developed by infogram and was uploaded with his permission. You can stop by his original post here. :)