Oh, and 99% of my driving is freeway, I activate the gear vendors at about 45, and it carries me up to 70 + easy, but I usually keep it at about 60. Hums right along. Before I had the gear vendors, it was screaming at 55. that was some serious long drives when you max out at 55!
I don't know if a 318 would have the grunt I need for my load when hitting the mountains or extreme headwinds. My robots and amps and merch is about 1500lbs, can't get much less of a load.
And, the rv now is totally gutted, no appliances or holding tanks at all. Just a plywood bench seat and some 1/2in plywood walls and doors. The 1x2 framing and aluminum shell makes the body very light.