i am considering converting to a 4bt in a 72 chevy 3/4ton 4x4 with a sb 400. this motor makes appx 400 lbs torque at 2500 rpm, i read a 4bt makes 300 or so,, my question i tow 5500 lbs a few times a month, wondering what the comparison would be power wise , why do you need a cummins designed clutch if there only 300 or so lbs torque..i know mileage will improve, i am runnning nv4500 and 3:73 gears right know wit ha 31in tall tire,,, all coments appreciated....