We use a simple chain but keep it out of sight with a box over the top when not in use.
Easy to slide it around the bed to point the exhaust towards open air.
Another option would be a mount on the 5th wheel pin-box. There is can be bolted in place and you can take the truck while the wife still has air/con in the 5er. The pin-box can easily support the weight. Get one of the fuel transfer rigs so you can leave a boat gas tank in the truck bed to feed it and you don't have to worry about lifting heavy gas cans (or just stand in the truck bed when filling)