It's been years since I've printed this but depending on the surface quality you want then can print bottom down with supports to support the top lip, or top down with no supports. I printed it in ABS. Sorry the initial orientation is not correct but just rotate it 90 degrees on the X axis to lay flat.
In the attached images I've vapor smoothed the part before hitting it with some spray paint. They have been sitting in the car for at least 3 years now and still look great.
This is the drivers side, but just flip it for the passenger side.
fc3svent.STL | 381.4KB |