A few things here that I noticed that have not been mentioned:
One: Put a fence between the track and the spectator area. I suggest something small like a 3' woven wire. I was a part of way too many pulls that the spectators were right ON the berms. I along with several other official/pullers spent the whole pull chasing people back off the berms. Put the fence 30' or so back from the edge of the track. Its close enough so people feel close to the action, but also have a safe standoff distance. Heck with just a fence put up concrete barriers! There is a venue out here where the track is down about 8 feet from the spectator area, several years back a tractor tipped on its side and pinned the guy between the dirt wall and tractor, not sure how to address that other than requiring roll cages.
Two: Put bleachers on both sides, up to about the 150' mark. From there, allow people to back their trucks up to tailgate the pulls. This always makes it lots of fun, and encourages the pullers to come up, mingle, and talk with the spectators. This helps bring people back for more events, and encourages them to stay longer, spending more money at your track. I would put bleachers all the way down as you just can't get the number of people in the back of a truck that you can a 6 row bleacher, of course this depends on the number of folks in attendance. Possibly bleachers all the way down on one side, and depending on the size allow trucks to park on the opposite side?? Plus sometimes the people parked in the back of the truck have too easy of access to alcohol to get totally wasted.
Three: Elevated PA/MC platform. Put the floor around 6' above the ground. Any higher and it’s hard for the drivers to talk to the MC, any lower makes it difficult for the MC to see what is going on. It may be a good idea to put a railing on the backside of this facing the pits. This way it makes a nice area for the drivers meeting. Put a roof on this too, it’s very helpful. Keep in mind, this need be nothing special. Make a deck 6' off the ground with electricity, a few fluorescent lights, a railing, and an angled tin roof. A folding table seems to work best for it.
Four: Not sure how big time you are going, but if you decide to go big time, you may want to have a remote kill system in place, setup on the MC platform. This saved our butts at one pull when the hook system on the skid failed.
Where is the land? If this gets built, I may have to come check it out!