In Indiana you can put whatever plates you want on whatever vehicle you want. I've seen Honda CR-Vs with 7,000# truck plates and F350 duallies with Reading bodies with 7,000# truck plates...they need an 11,000# plate on that. But since nobody cares, who cares?
Indiana makes a lot of money buy selling license plates. Whatever your spin is, they offer a plate for it. My E350 needs a 10,000# truck plate, but I have a children's hospital plate on it. I have a Marine Corps veterans plate on my Harley, and a Kid's First plate on my Ninja 1000--the proceeds build playgrounds for inner-city kids.
If you are talking physical difference between an F250 and F350--it's just a little bit stiffer springs on the F350. The same is true in all modern trucks from the big three. The dually kit is only avail. on the one-ton, but the 3/4 or one-ton with the single axle will tow more because it weighs less. It's the same exact axle--just a different amount of tires. Even a 30,000# car hauler is fine on a single tire truck--4,500# tongue is no problem with a gooseneck. It's less than a cube of bricks in the bed. It dosn't matter what the rating is on the truck--it's what rating you bought from the BMV. And if your license is suitable for the DOT.
In the past, Ford was the only honest light-truck rater. Chevy and Dodge had 1/2-ton semi-float axles on trucks and vans with 3/4 badges. With the exception of that weird 7-lug F250 in the late '90's, Ford always had the real gear on their 3/4 and 1-tons. Except for their later vans. Mine is a 2000 and has a full-float rear axle, but 3/4 and 1-tons later than mine have semi-float Dana 60s. Even some E150s have that axle. A semi-float axle has no place on a 3/4 or 1-ton. My wife's 2500 Mercedes Sprinter has one. You get one bearing, and the axle shaft is carrying the weight. The shaft flexes and the bearing squirms. And dies. A full-float is like a trailer. The axle shaft carries no weight, and it has 2 larger bearings on a big spindle that does the load bearing. It can carry anything. They don't fail. Ever. You can't break it by overloading it.
Take off the hubcap. If you can undo a circle of bolts and pull the axle shaft out without removing the wheel, you have a real truck--period. I don't care what the badge says. Load in pallets of bricks, playground sand, or concrete mix. Won't ever hurt it.
Any F150, the GM 8-lug 1500HD and such--yeah, you can carry such a load once in a while. But it's not going to last long doing it for a living.