One of the crappy things about cabover trucks is there is no "rocker" to put slider bars onto. On my 4Runner, I had sliders welded to the frame and could rest the weight of the truck on them to pivot around obstacles if required. I know this is not a rock crawler and Matt's won't be either (if it ever gets finished), but that was an issue that we discussed several times since there is such a large area between the back of the cab and the rear wheel.
I think 19" of ground clearance should be plenty. Are you going to make some kind of skid plate or slider to protect the underside of the tank?
I need to get up ther and check out the shop before it is 100 degrees out...
Looking good man.,