sheriff.yft, sheriff.ytd, and sheriff_hi.yft go here:
Grand Theft Auto V\update\x64\dlcpacks\patchday9ng\dlc.rpf\x64\levels\gta5\vehicles.rpf

carvariations.meta goes here:
Grand Theft Auto V\update\x64\dlcpacks\mpchristmas2\dlc.rpf\common\data