Open OpenIV or Codewalker RPF Explorer and 
go to mods/update/x64/dlcpacks/falken/dlc.rpf/x64/levels/gta5/vehicles/vehicles.rpf and open falken.ytd and 
click import and choose falken_sign_5.dds (make sure you drag it to desktop or where ever you place it before that) 
and click open and then save and that's all.