I would stick with the NV4500. Parts are harder to come by for the 5600, they are bigger and may be a little harder to work around, and there will be brand new aftermarket NV4500's on the market soon. Not to mention the substantional price difference in the two.
A forum community dedicated to Dodge Cummins Diesel truck owners and enthusiasts. Come join the discussion about reviews, drivetrain swaps, turbos, modifications, classifieds, builds, troubleshooting, maintenance, and more!