Call (1-888-943-8287) and ask for Junior at ATSsprings.com as he knows exactly what you need.
There is only one OBS (the body style you have) front leaf rate for the F350.
I had an old set of front leafs that someone put a helper leaf under it. I just replaced them with new leafs from Junior. With freight to my door, 4 new U bolts and 4 new mount bolts the bill was still under $400. The ride is much softer and I only lost about a 1/2" from the helper leaf setup. I have about 3" between my axle and the rubber bump stop. I'll measure for sure tomorrow.
I believe that DOT makes blocks up front illegal. But, Junior can help you with what they call "zero rate" leaf. It is not a lift block because it it bolted as part of the leaf pack. A lift block is not bolted to the spring pack. This will give you another inch.
If you really want to lift it, even if only 2 inches or so, you can explore a RSK or Reverse Shackle Kit that lets you use Superduty body style ('99 and newer) front leafs which have a variety of spring rates for different loads or ride height.
I'm not on this page very often so if I don't respond please send me a private message.
Good luck!