install the car in:
update/x64/patchday10/dlc/x64/level/gta/vehicles.rpf

Install tuning in:
x64i/levels/gta/vehiclesmods/serrano


To make the livery work you need to:
4. Edit "vehicles.meta" in update\update.rpf\common\data\levels\gta5
		
Search for "<modelName>serrano</modelName>" and then Search down for "<flags>" and add: 

				FLAG_HAS_LIVERY