I have used an HDR image only in the max environment for the reflections. Fake caustics from the rims I have created a spotlight for each rim for this purpose and enabled the inverse square decay ? simply put, this makes the light lose power with distance. In the advanced effects rollout, I have added a monochrome noise map in the projector map slot. This makes the light project? um, light only from the white area of the map. I cannot tell you how to create this map as it depends on the shape of your objects that are causing caustics and mine are totally incorrect anyway. You can always use real caustics instead at the cost of rendering time.
When you have done this, turn the plane into an "Editable mesh" object so you can begin modelling the car. If you want to you can give the "Plane" another name like car or body...