Re front springs: I'm pretty sure the Ford coil springs parts are the same for 2005-current and are interchangeable between F250-550, with one set for each for 2wd and 4wd. So prob the same applies to aftermarket.
For the above listed trucks Ford has nine linear spring rates made to be used at the same design load height (within the oem geometry) the choice of would usually dependent on application load. In practice that might give an owner who, even after purchase wants a little softer ride or to compensate for added weight, the option of going up or down 1 or 2 spring rates with an oem part (if they are ok with oem). I see that as a real plus worthy of mention. For something/someone else, there may be aftermarket suppliers.
For the above listed trucks Ford has nine linear spring rates made to be used at the same design load height (within the oem geometry) the choice of would usually dependent on application load. In practice that might give an owner who, even after purchase wants a little softer ride or to compensate for added weight, the option of going up or down 1 or 2 spring rates with an oem part (if they are ok with oem). I see that as a real plus worthy of mention. For something/someone else, there may be aftermarket suppliers.