Is there a 5-3 GB version of 2.7 in x264 MKV format?
Find Chewtobacca’s DVD5, mount the ISO, and use MakeMKV to create your new mkv file. Unless you really want the difference in resolution, this would be the simplest way to do this.
If you want any more audio options, you can take the any of the audio files you want from the original mkv version and mux those in using MKVToolNix.