I recently stumbled across a game called Drag Racer V3. This game not only gives you an extreemly wide array of parts, it gives you a large variety of cars each with unique ones.
Much like the new jewel system brought in by The Burning Crusade, the cars in DRV3 have different tuning options and slots that are better for some cars and worse for others. But unlike in the Burning crusade they pretty much all look cool.
I played DRV3 until i had a Mclaren f1 that could run a 400m sprint in about 3 seconds. If you are a graphics junkie, peddle your wares at another convineince store. This game is artistically well done, but no super anti-triple-aliasing buffer squadrons.
Well there you are, play up. see if you can beat my record of the 400m dash in 2:56 secs @ 670 mph. Good luck.