Here are some building tips for large scale car interiors. One major thing is to eliminate studs from your interior. Besides the floor, you should cover everything in your interior with smooth pieces. Also try to make seats that can tilt backwards and make details like gloveboxes.
About this creation
The dashboard is a key part of the whole interior. Try to make a dashboard as realistic as possible. Suggestions include a navigation system, air vent(s), glovebox, foot pedals and a speedometer.
The tilting air vent has to be my favorite part of this whole interior. I got the idea when I was making the tilting steering wheel. Remeber the details are what make a car look good. I like to keep things simple at the beginning and make changes from there.
When I was gaining inspiration for my second large scale car, I noticed that foot pedals were a detail many people put into their cars. I gave the idea a try, but the foot pedals are not in scale with the rest of the interior.
I salvaged these seats from my 4993 convertible. I belive seats are the hardest things to make in a car interior. Perhaps the easiest way is to modify seats salvaged from a Lego set.
The center console is also a very important part of the interior. Mine is not completely realsitic but I had to find a way to fill the 4 stud gap between the seats. Try adding cupholders, a shift stick or even air vents to your center console.
Back seats are just as important as the front seats. Back seats make your car realistic and also make your car interior look better. I didn't make a back seat for my mustang and now after I took in apart, I regret not making one.
Here's a shot of a complete interior. Putting everything in place is just as important as building an interior.