The F250 and F350 have the same springs. The F350 has an overload spring in the rear. The F250 does not have the overload unless ordered with a heavier suspension group (i.e., camper package). In that case, that there is a heavier suspension package, the springs, including the overload spring, are the same. The only difference then becomes the block height under the rear springs. The front springs are always the same between F250/F350. The fronts only change between option groups or engine, but not because of whether it is F250 or F350. An F250 and F350 ordered with the same engine or options will have the same front springs, the same rear springs and if ordered with the camper package (as an example) will both have the same overload springs and sway bars.
The "off road" shocks with the off road package are just Rancho "branded" shocks. They are made by the same company either way (Tenneco if I remember right). If you're going off road, the value of the off road package is the skid plates, not the suspension components (shocks).