You can replace his normal model in world.img or in ide.img (harder way but cleaner).
Just change the name in world.img?
There are 2 ways.
If you want to make him appear editing world.img then you just have to swap names (using the rename option) between normal gord and _bw gord, both .nif and .nft. Don't do this with the cs_ version of gord since this is his cutscenes model and can make the game to stop working.
In ide.img you have to swap names too, but since you can't delete nor add extra characters in this file, you have to use the code swap method.
