Sub 20' Class C - Ford 5.4L 5 Spd or 6.8L 6 Spd

We have a 20 ft 2004 Adventurer former rental with the V8. It just has L, 2 and Drive plus the tow/haul switch to turn off overdrive. I have no complaints on its power even in the mountains. Other than tires and brake maintenance it hasn’t been in a garage or RV shop in the 11 years we’ve had it. It has about 115,000 km and no engine difficulties - it’s getting a new serpentine belt next week only because I figure it is probably in the middle of its life with us.