Hi Joel,
This is a problem you will often run into and one you need to master. You mention the room is too big to light and still you must try to counter the strong light coming from outside. When I run into this, I light as well as possible, the subject (in your case I guess its one or more cars)and then stay tight enough to be able to use your f stop to light up the cars. If you shoot wide with a low f stop like f2, your outside background will be all blown out but if you can stay tight enough not to see too much of that, it will work. Shoot your important shots like that and then if you need a wide shot, you will have to allow for some compromise. Concentrate on getting the important parts of the scene looking right and the client will be happy. If the client wants both, show him on your monitor what happens at the different f stop settings so he understands.
Good luck
Doug Wiggins
Video Innovations
Sydney, Australia
https://www.filmu.com.au