Where are the model files for the Sheriff Cruiser located?
I found some in x64e but after replacing them with another model the car in-game isn't changed.
Also is there a thread telling us where certain files are located? Because I looked through the forums and couldn't find any.
You can search for specific cars in OpenIV by pressing Ctrl+F3 ('Tools' tab > 'Search'' is another way).
Are you looking for Sheriff.yft/.ytd etc?
If so, it has 3 locations in my game:
\mods\ x64e.rpf \levels\gta5\vehicles.rpf\sheriff.yft
\mods\update\x64\dlcpacks\ patchday1ng \dlc.rpf\x64\levels\gta5\vehicles.rpf\sheriff.yft
\mods\update\x64\dlcpacks\ patchday3ng \dlc.rpf\x64\levels\gta5\vehicles.rpf\sheriff.yft
You want to replace the newest version of the car (usually the highest patchday?ng number). In the examples above it would be the one in patchday3ng. If you don't have patchday3ng, then try patchday1ng & then x64e.rpf. In that order.