The biggest issue is no matter what axle you put under the back end, your truck was certified as an F250 when it left the factory. Sticking an F350 rear axle under the back means you still have an F250 and can only legally carry that weight. I can't blame you for not wanting the payments of a new truck, but who says you have to have a new truck. BTW hauling a fiver, DRW is the only way to go IMO. Brought mine home today in 40-45 MPH cross winds and was rock solid.