Ride heights

So I'm coming from asphalt racing going to dirt racing and I know nothing. I picked up a car and I'm attempting to find any sort of setup guidelines. I contacted the manufacturer and they are being jackasses in refusing to help me. I need to convert this car from a 4 link to a 3 link but I want to put it to a good base ride height before I get started. Can anyone tell me a starter point for ride heights? My online research tells me 7 7/8 and 8 inches on the front. But on the rear most of them measure from the top frame rail to the rear end housing and it's hard for me to do that because this car may not have that top rail in the same place. On asphalt I just measured from the ground to the bottom of the frame all 4 points it was simple...