High ride height is ok, shocks must be set almost or equal and stiff,spring rate shouldnt be much different from tarmac values perhaps just a little softer, for oversteer might recommend to set the rear stronger but no more than 1.0 also a stronger front stabilizer helps lets say 6/4 as an example,set camber to 2.8 both front and rear.
I would suggest a 50% VCD as you need the most grip at dirt tracks.
Remember that the more you increase the power the more unstable a car would be so different values would apply for each tune level ,also having no downforce means some disadvantage when racing against race models.