depends on the suspension type within the vehical...
what you'd do is calculate the height of the 4 wheels, then add to that the bellcurve for the suspensions reaction (crossproduct if they're not wishbone suspension)
you then calculate where the CG of the vehical would be, which is the crossproduct of the wheelbase (distace between the wheels, both on X+Z)
then the center of the actual mass ... you then take the crossproduct of those two values and Add it to the original CG value (which should offset it to the rear of the vehicle slightly)
like so CG.Y = CG.Y - (((tensionOfSuspension + WheelDiametre)+ CG.Y)/2)
that should be basically all you now need to do this on a basic scale...
Tsu'va Oni Ni Jyuuko Fiori Sei Tau!
One block follows the suit ... the whole suit of blocks is the path ... what have you found?