Ha. I love that Jimmy is on notice, but has traditionally been the one I've seen post the most Warehouse23 links for folk to go and buy. Even when I would ask for a rule quote in a private email, he'd still send the W23 link.
But YES, some of those boat and tank and chopper maps are GREAT for off-roading. Water depths, gullies depth, etc., can sometimes be too rough for off-road cars, but you can change any values you need to make the map terrain work better for you.
http://www.warehouse23.com/products/boat-wars
http://www.warehouse23.com/products/car-wars-tanks