Considered one berm with a 300 yard reach, or 500 yards if you can. All you really need is a strip to shoot through with long range rifle, then have it open up at the pistol distances you require.
I have my own range. It is split into two locations, I don't have a ranch, but just a few acres to work with.
Pistol berm is only 8 feet tall at my house. Rifle range is accross the street in a hayfield. Again the berm is only about 8 feet there. I mow a strip down the field, and poison a little circle of grass at 50 foot intervals for a quick distance measure, and just shoot prone from between 50-350yds. I don't own the hayfield, but have permission to shoot there, maintain my "shooting ally" and to build the berm in the back. I can't do anything like a bench, cause that would interfere with the hay production.
Good luck, I've got a thread on here somewhere with some construction pics. North facing is great, my pistol bay faces south, but I have large trees around, and behind so it's not a big deal.