I've used these files to change the names of clans as follows for customized (unhistorical) Sengoku campaigns:

[i]-Shimazu - unchanged.
[ii]-Mori - changed to [1] Yamana or [2] Amako.
[iii]-Oda - changed to [1] Hosokawa or [2] Asakura
[iv]-Imagawa - changed to [1] Hatakeyama (too long) and then to [2] Akamatsu.
[v]-Takeda - unchanged.
[vi]-Hojo - [1] left unchanged or changed to [2] Ashikaga in all unhistorical campaigns.
[vii]-Uesugi - unchanged.
[viii]-Tokugawa - same as Imagawa above.
[ix]-Toyotomi - same as Oda above.
[x]-Date - changed to Uesugi.

It takes alot of time and patience to change clan-names. Backing up these files in appropriately named backup folders when not in use is greatly recommended or your work could be lost, (especially if one installs a custom campaign like Terazawa's Gempei campaign which, when uninstalled, restores the Loc.txt files to their original stock forms only).