1: Install this mod:
https://www.gta5-mods.com/vehicles/brute-tipper-based-mixer-classic-add-on
2: Extract the "mixer3_sign_12.dds" file
3: Using OpenIV with Edit Mode enabled, add it to "E:\SteamLibrary\steamapps\common\Grand Theft Auto V\mods\update\x64\dlcpacks\mixer3\dlc.rpf\x64\levels\gta5\vehicles\vehicles.rpf\mixer3.ytd"