It's been my experience that the game assigns point to the race based on how competitive you are with the other cars. For example, the first few races I ran were in a very un-competitive car, and I was getting 70 to 90 points a race. After I upgraded the car and was in a position to open a can of whoop-azz on 'em, I got 1 or 2 points a race.
I'd guess racing in a pickup would qualify for some serious points, but so would a Vitz.
Chuck