Have you looked around in the car forums?
I found this:
http://www.rcuniverse.com/forum/m_9413639/tm.htm
Hope you don't suffer from motion sickness...
There are several forums you might try searching in...in the car and maybe tank forums?
I would think you could build something pretty nice for 1000 bucks!?[8D]
Maybe a Stadium Truck...say around 1/12 or 1/16 scale? They would be small enough, yet not too small...have enough ground clearance, and 4 wheel drive. You can use dirt track tires to deal with potentially dusty ductwork (traction on slippery surfaces )