Let me jump in and say I just did a conversion this weekend. With all the troubles Chrysler was having and the economy I was able to a steal of a deal on 4x2 09 Unlimited X so I went for it knowing I would do the conversion. In all honesty it was a very easy thing to do. I have a close friend who works in the parts department at the Jeep dealership so I was able to get all my parts at cost. I went ahead and swapped in the Rubicon rear axle assembly as well.
Here is what I did and what you will need:
I got the front rubicon axle assembly (D44) without axle shafts, steering knuckle, or anything. Basically, it was the differential and empty axles tubes only.
I got the rear rubicon axle assembly (D44) the same way, just the diff and axle tubes.
I ordered chromoly axle shafts for the front and rear from Northridge.
Everything from the front and rear axles on the 2wd transferred right over. The brakes, hubs, steering knuckle, etc.
You will need to wire your elockers on your own and I just bought some of the nice looking ARB style switches and wired them up inside.
You will need a couple axle nuts for the front axle shafts since your 2wd didnt have any.
You'll also need the 4wd tailhousing or adapter as Jeep calls it. It replaces the 2wd housing.
You'll also need the 4wd tailshaft (actually its a spud shaft) and it just slides right on the output shaft of the transmission.
You'll need new front and rear driveshafts. I got the coast driveline shafts from Northridge.
You'l obviously need a transfer case. I chose to go with the Rocktrac and I intend to add the Rubicrawler soon.
You'll need the transfer case shift cable and shifter for inside the cab. You'll also need the 4wd bezel for your center console so the shifter will fit through and everything will look stock.
You'll need transmission fluid because you'll lose a lot when you pull the 2wd housing and of course you'll need gear oil for the new differential.
I also installed the teraflex frame brace and draglink flip kit, JKS quick disconnects, JKS rear endlinks, JKS ACOS, EVO axle sleeves and gussets, JKS rear trackbar bracket, and EVO KING shocks.
It took me three full days to do the conversion and install all the other goodies. The total cost of JUST the parts from MOPAR (axle assemblies, 4wd adapter, t-case, spud shaft, tcase shifter and cable, console bezel, and axle nuts was 5K. I bought the Jeep new for 17K and by the time I'm all done I will have about 9K into it total so I have a 26K Jeep thats way beefier than a Rubicon that would have cost me about the same.
Yes it was a lot of work but I had fun with it I can help with part numbers and installation if you need any. Feel free to ask questions.