Sounds like your going to be hauling heavy and often. If that's the case, and I hate to say it... buy a duramax. Then you can have mutiple tunes so you can haul your cattle trailer around, then unhooking and turn a knob and unleash the beast! You said your willing to sacrifice HP for tq. How about 900 ftlbs with a stock Turbo and drive train? I think you will spend alot of time worried trying to tow heavy loads on hot days with the Turbo gasser. I'm no F I expert tho either.