YOU MUST SET YOUR CARCOLS TO TAN IN ORDER FOR THE DIRT TO LOOK RIGHT. 
Replace one of your colors (I used a yellow, number 38) with these RBG values:
155,143,112

Delete all Mesa carcol values and replace with that color. ex:
38,38

Replace your Mesa Grand line in default.ide with this:
230, mesa, mesa, car, DESPERAD, MESA, null, normal, 10, 7, 0,  249, 1.0

There were no other handling modifications done.

YOU MUST HAVE DMAGIC's WHEEL MOD INSTALLED IN ORDER FOR THE CUSTOM WHEELS TO WORK