Al, I did a complete spring and axle swap. The F350 springs will move you about 3 inches off the bump stops, with the add-a-leaf's, I have about 6 now. The ride is much better than my stock F250 springs, but they were about one inch from the bump stops and hit them about every bump. Personally, I would not hesitate to use the add-a-leafs. You can also get leaf springs reasonably at two places I know of and I bought springs from both. JCWhitney has a pretty good deal on them and since they are over the $150 mark, you can get 15% off (a deal they run quite often). Also, Black's Springs in Zanesville, Ohio. They used to discount to me at the parts store and would probably do the same for you, although it has been a while since I did B2B with them. I just purchased one rear from both and they were almost $ for $. My rear springs were about $130 each but they are 2 1/4" by 10 springs. Fronts should be much less. Personally, I don't think Ford put enough spring on the front of these trucks stock, so the add-a-leafs get them closer to where they should be.
Just my .02 worth I guess. I really like the add-a-leafs on the front. I remounted my whole rear end so I allowed for the additional ride height of the front, still sits slightly lower in the front and I like it slighty that way.