I found these models in one Garrysmod mod what made by mod maker TFA, and recompile them for older half-Life 2 engine so they can be used in SMOD.
Also they was not sized to fit NPC proportions and was big, I scaled them down almost twice, but maybe they need some proper scaling for better fit NPC proportions, also eyeballs need more boxy physboxes because they constantly emit impact sounds when rolling around. About scripts/npc_gib_model.txt if you use me combine gibs mod, open it in notepad and copy "default_humans" section into yours, if you just drop and overwrite it will discard combine gore gibs.
Also if you check my Advent Pistol release you can see on video how these gibs work on citizens.
Link (Model source in SMD included too):
https://www.dropbox.com/s/ijpw335am9014uy/fonv_gibs_models.rar?dl=0Mirror:
https://drive.google.com/open?id=12EbCBeegPvpliY4X8d71s2j-tlzsL_FnScreenshots:
http://imgur.com/a/z1EAT