This is the route I went on my crewcab. Found a complete donor for a steal! I ended up selling off what I didn't need...which paid for the truck. SO I was left with everything I needed for the 4wd swap for free!!What you'll need (not exhaustive):
Steering hardware (drag link, etc. dunno if you can use your steering box)
Front drive shaft
Rear drive shaft cut down
*Sourcing this stuff may cost more than a donor vehicle
What you'll need to do:
Lots of work, followed by
Lots more work
But hey, I say go for it because I enjoy building vs. buying.
But it is a big job!! You can check out my build thread in my sig to see what it takes.