for towing I would say twins is the way to go...if your pump is tuned to 500hp though, keep your foot out of it towing that heavy...while the engine will pull just fine, the cooling system will not keep up with that power level indefinitely. its just too much heat for the stock cooling system and temps WILL go up. long as you have common sense on the throttle you will be fine.

if not, then you might want a bigger triple pass radiator

 

Triple pass radiator? Explain... I wanna upgrade the cooling system so it runs without worry of overheating lol! I will probably end up going with a ZF6 as it has a integrated oil pump that you run to a radiator for cooling purposes.

 

triple pass radiator = radiator divided into three sections...coolant snakes through the radiator in a S pattern...top middle and bottom are separate sections. coolant in the middle flows opposite direction of the top and bottom. forces the coolant to stay in the radiator longer for additional cooling before returning to the engine.