2015 F250

I haven't found it to be the case that 250's have softer springs than 350's. Usually the overload spring is standard on the 350 and optional on the 250, but the rest is the same. The 350 is raked 2" higher by using a a taller axle block. This allows more spring compression without looking tail heavy although drive quality is the same. Ford uses lower rated tires in the base 250 verses 350 that derates the axle capacity - This can also be optioned to higher capacity. What you will not see is this additional capacity reflected in the door tag since the truck is constrained by the Class 2B limit of 10K lbs GVWR.