Very similar axles between those two trucks. Both of them have a high pinion Dana 60 front axle. The Dodge will have either a Dana 70 or Dana 80 rear axle, depending on engine and transmission choices. The Ford will have an Eaton (sp?) 10 1/4" rear axle. So the rear axles will have ring gears that are within 1/2" of the same size, with axle shaft diameters that are essentially the same as well.
When Phord went to the new Super Duty body style they cheapened up their drivetrain though. They now only have a Dana 50 front axle, instead of the Dana 60 they used to have. I have a friend that broke his new Super Duty Phords front Dana 50 pinion shaft right off when trying to move a very large trailer one winter moring. The trailers brakes were frozen solid, and he was just slowing applying more and more throttle to his Powerstroke diesel motor, with the truck in four wheel drive low range, when ... BANG!!!, broken front axle pinion shaft.
MoparToYou.