1997powerstroke, instead of getting f450 springs you'd probably be better off buying heavier OE replacement springs from a manufacturer. I'm waiting on getting some 3 leaf springs (rated 800lbs over stock) for the front of my truck. They're made by a real large manufacturer in Canada called Standens.
As far as lift goes if your truck is a 4x4 and you haven't done an axle swap you have the Dana 50 ttb. This is a some what independent axle that pivots from a center mount. You can't properly lift your trick without dropping down the mount where the arms pivot. But with heavier spring it may pick up the axle a little and it will help if your tires have a negative camber (/ \).Also if your are dealing with negative camber it may be time to replace the ball joints, pivot bushings, and shackle bushings.