the swap presuming you have an automatic transmission:
1. 4wd transmission or at rebuild time have a 4wd output shaft installed & purchase trans to t-case adapter
2. transfer case - manual shift t-case with all shift linkage will be the easiest
3. t-case shift boot
4. wiring harness for 4wd indicator lights - most of this wiring is already in your truck you just need the very end that goes to the t-case and this is only if you want lights
5. Front axle - I would suggest for ease of installation purchasing a solid axle from an F-350 w/ steering, springs & spring hangers Hopefully with gear ratio matching your existing rear.
6. Drive shafts, Front & Rear
7. drop pitman arm from F-350 if using that axle
8. F350 rear blocks (1" taller than F250) to bring rear up to proper height w/ front
9. 4wd trans cross member & skid plate
10. 4wd shock towers
It is time consuming not overly difficult all holes are there in the frame for you to attach everything to, you will need to clean up the brackets from your I-beam suspension. And depending on how you go about the swap and buying pieces & parts it can be rather expensive or inexpensive if you have space to buy parts over the span of a year or so then you are likely to be able to find deals if you keep your eyes open on the big ticket items. One benefit of being in OH is that 4wd is far more common and the salvage yards are less likely to think that it is made of gold, maybe only gold plated. As far as time is concerned I have done 4wd conversions including custom fabrication in a 3 day weekend, granted I had all of the parts and pieces I needed and it was all labor.
