The Bilstein BTS system is very good.....however it has been on backorder for quite some time (we took it off our webstore until it's back in stock).
Icon is going to be by far the best riding system....but also more expensive:
Icon Vehicle Dynamics 2005-2008 FSD F250 2.5 inch Leveling System - 2005-2007 F250/F350 SRW 4wd - Truck Toyz Store
Note: this is a F-250 system so it already includes the larger rear blocks and u-bolts.
Another option would be the RCD system...which rides well, just not as nice as the Icon:
RCD 2.5 Inch Suspension System - 2005-2009 F250/F350 4wd - 2005-2007 F250/F350 SRW 4wd - Truck Toyz Store
(note: with a F-250 you will need larger rear blocks and u-bolts to maintain a level stance....they are in the rear lift drop down menu on the page).
Of course as always we have 0% for 90days on all purchases if you use the Truck Toyz/Car Care One card.