The wacky axle I've got on my F250 is apparently a super duty axle. If I install one ton springs and a class V hitch then I have all the equipment (but not the legal weight rating) of an F350, and then some. My rear springs need replacing anyway, and the ideal would be to find super duty springs, but I assume they're in short supply. The alternative seems to be to get rear lift springs, which is a somewhat spendy proposition; indeed, they are almost as expensive as the rest of the lift put together!
I found this out at Hahn Automotive, where I was picking up a 1962 Streamline "Duchess" 22' travel trailer from the owner on behalf of my lady, who has never towed anything, nor driven my Ford which is the only vehicle around here with a hitch on it right now. Even if another vehicle had one, the trailer would need the brakes reinstalled to be towed by either; one is a 2000 Astro and the other is a 1982 Mercedes 300SD. The Astro has plenty of power, but not enough weight to handle the trailer without brakes. The Mercedes has neither qualification; it has barely enough power to get it here, slowly, and not enough weight to make it safely.
While I was there I let them replace a U-joint, which turned out to be the source of a thumping noise on acceleration which I thought was related to the center bearing which has been replaced once already. But before towing the trailer I got down and checked it out and it was pretty well shot. We only found out that it was a super duty axle after the wrong bearing was delivered twice and the owner had to run to the parts house himself to get a replacement in a timely fashion. As it is, I ended up spending most of the day there with one thing and another, with a brief stop by Carlos' Country Kitchen which is just around the way from the shop. Pretty good biscuits and gravy, but the biscuits could use a little more loft and possibly cooking time.
While I was there I spotted an F250 Super Cab Longbed Powerstroke in the old body style (like mine) with the same size and brand of tire, and the same Rough Country lift. Very amusing.