Don’t know what you mean by “track him around or in front of the car”. Is the BG in Max as well? Is the camera orbiting around the car? All of this matters.
If it’s just a front shot then just shoot the actor on blue screen, key him out, load this clip into Max with an alpha and apply him to a flat plane inside your car.
If the camera move will show perspective, then on set shoot your actor on a keyable BG with small dots on the walls so that matchmover can make a 3D track. Also set up C stands with tracking points between the subject and the walls so there is more depth data for the tracker. Use this tracking data in Max to render out the car at the same angles. Then render out the alpha of the car windshield to use as matte for your keyed out actor. Then render out separate reflection passes for your car windshield and lay them back on top of your actor.
There’s a LOT more to it than this for an ideal composite, but this is a basic idea.
Chris Smith
https://www.sugarfilmproduction.com