Y'know Feets, I think you'll do just fine going the TQ route. I've had a 24 ft RV with a 440, and I have a 28 ft one with an injected 460. I thought the 460 would at least be equal to the 440, but it's 3-4 mpg less. Yes, the newer rig is a bit heavier, but not 3-4 mpg heavier. I would think that if a genuine smogger 460 can get 9 mpg pulling a 9-10,000 lb motorhome around, a well thought out 440 could knock down 15+ mpg pulling a sleek 5300 lb Imperial around. Even one breathing through a good ol' Thermobog. Please tell us you're going to use a proper Mopar dual snorkle air cleaner assembly, with the vacuum actuated flapper door.