Rear 05+ bolts onto factory leafs. Have to build new axle side shock mounts (I have the dxf file from mine, happy to discuss making a set for ya on the plasma table). 05 rear sway bar and end links bolts right up. Rear diff speed sensor gets swapped for OBS axle to 05 axle. Need an adapter for the brake hose fitting. (Can't remember size off hand) use 05 softline.
Front- I used a kit from Ryd Motorsports. Basically adapts the 05 suspension to the OBS chassis (radius arm bkts, coil buckets, sway bar bkts, and panhard bkt). Uses Ford radius arms, 05 sway bar, etc. Kit is much easier to install on 4wd truck (holes drilled already). RYD definitely caters to the big gay truck crowd, but its pretty beefy stuff, customer service is a solid meh. Can't go much lower than mine sits in front without reworking their panhard bracket (gets into diff cover at full bump, could probably be clearanced to get more up travel).
Steering- 05+ box bolts on in stock location. Steering shaft slips right on. Need a pressure hose from a 99-03 7.3. Return line is easy.
I'm happy to do a full write-up build thread if y'all would like? I can show the good and bad of the RYD kit and explain what should be done different if anyone wants to do the swap themselves..
Edit- if you're gonna go through the hassle of drw swapping, do yourself the favor and do the 05+ swap. Rides great, parts are just as cheap or cheaper and easier to find. And its fucking BEEF