I wouldn't suggest mounting it on your dash. It will make your truck too tempting of a target for punks with sticky fingers. I've lost so much radio equipment to auto burglaries. If you DO mount it up there, I would suggest taping razor blades to the lower back side so the little punks will lose their finger tips when they try to rip it off your dash (can you sense my bitterness?).
Also, if the thieves don't get it, the Oklahoma sun will.