Sounds like you'd be happiest with something like a trail truck with a decent powered system in it and some scale-ish mud tires.
I'd suggest taking a look perhaps an Axial SCX10 as a base vehicle, then swapping out the tires, wheels and body for some 2.2wheels with Imex Swamp Dawgs and body of your choice.
Axial SCX10
http://www.axialracing.com/ftp/scx10/
Imex Swamp Dawgs
http://www.imexrc.com/servlet/the-28...G-TIRES/Detail