The Kaibab Forest is a working forest. There are lots of forest service roads through out the area. We were able to drive over to an area called Temp Point and pitch a tent on the rim but there are many such areas along the rim. When we were there, these "developed camp sites" were really nothing but a slightly cleared off area where one could pitch a tent under the ponderosas. However, like I said before, you can camp anywhere inside a national forest.
Highway 89 at Jacob Lake, AZ takes you to the entrance to the North Rim. Along that 40+ mile drive, you will see several forest service roads leading to right and left along the road. The best way to find your way is to stop in Jacob Lake at the welcome center an ask a ranger or buy a map of the Kiabab Plateau. The rangers can also be called ahead of time to check on road closures. If you are still planning on mid-March, I bet the roads may be closed due to snow. The Kaibab Plateau is at 8000 feet (2400 meters) and snow tends to hang around at that elevation. My wife has taken a picture of me standing in 8 inches of snow in the forest in mid-May!
Hope this helps,
Search the net for Kaibab National Forest and you will find phone numbers and map ordering info along with other info.