Keep in mind boys, longer the truck, less payload to play with. These trucks don't hold a lot of weight, and water is heavy and everything can add up quickly. I have an 2005 isuzu npr with a 14ft box. Small pressure washer and burner (I lifted both in separately, but the burner is only 240,000 btu's), inverter genny and 200 gallons of water and I am over weight with full fuel tanks.
3500/350 and 4500/450's good if you can fill up at site, if you need to carry 4 hours plus worth of water look for a bigger truck or a trailer to pull behind.
Just sharing my mistake as I didn't figure this out until after I had installed everything and had been using it for awhile.
Truck looks great though!