Cant just travel anywhere you want with guns, so you had better check on that one.
Add a large solar cell to the roof to charge batteries while the van isnt running.
Put two large batteries on an isolator switch to switch between them incase one dies, and use one for the fridge, tv, etc.
Ham radio on 2 meter band is a good idea, and a cb radio also, and find out which carrier covers the areas youll be in the best, or the country/world. Get a 4 band cellphone.
Wireless internet and a laptop.
Maybe headfi members in different states will let you shower?
Puplic pool areas, and some beaches have showers, and camp grounds/parks, which are cheaper than hotel/motels.
Keep foods that dont have to be kept cold.....peanut butter, pasta,oatmeal,meat sticks,bananas,nuts,canned beans,etc.
Tools, tire irons, etc., make good weapons.
Carry a passport and a drivers license, incase you need extra picture ID.
Gyro-crank flashlights and radios are good so you dont have to buy batteries.
Build some storage units on the walls,etc., so you can store things and they wont slosh around the van when youre mobile.
Get an 18" dish for TV. They make mobile van versions.
Get a truckers mobile cellphone antenna for increased reception. Check companies like Wilson for that.
Get a watch dog as a companion and to watch the van while youre out or sleeping etc.
Something that wont take up too much room, but strong and intimidating, like a pittbull.
If you get the pitbull, check to make sure theyre not restricted in some states first.
Of course its also good to have 2 GPS's. ...TomTom for the Tele Atlas maps, and Garmin for Navteq maps. Each are good in different areas.
The top of the line TomTom has something that enables it to track without a signal for awhile in cities and tunnels etc for a short time.
Also, bring a bicycle incase you get stuck or want to take a ride in a town or something on a nice day.
Tarps and rain gear is always a plus and a good weather radio.
Large First aid kit, and locations of hospitals in the area.
Large flood light to work on the van at night.
Habatchi or similar BBQ and an awning built onto the van and a folding table and chairs for outside dining.
Water purifier and a large water tank so you can fill up at rest stops.
Start an internet biz to make money while you travel. Then you can run it from anywhere.