Try some thing simple save out your car as a ps file and another file for your background, in photoshop with the car on top of the background just play about with the capasity and fill to help blend...

If you have photoshop or after effects its better to comp out in one of those ........dave

Looking good Acid, the last one the background looks like a matt painting you could try a zdepth pass or blur filter to bring it together, I think Tom would have liked the idea of people using his...