This guide will provide you with the location of benny’s workshop in Grand Theft Auto 5.
You will need to open up the map and you will find the garage icon on it on an online day, it is Benny’s garage.
You can do a mission when you get next to the building and can also customize the vehicles.
You will not find it in the story mode. But you can also go to Benny’s website and navigate to Showrooms. Choose the vehicle and then you can customize it.