Like Vile said it is allot of work but probably your best bet to find a good running gear / frame and swap your body etc.
To convert yours you would need a matching gear front axle, & tranfer case as you mentioned. Plus a 4x4 transmision or swap the out put in your 2x transmision, drive shafts, trans cross member, 4x4 shifter, 4x4 spedo cable, The center floor hump from a 4x4 or a 2" body lift, the rear spring shackles, front leaf spring shackles, front springs, 4x4 engine cradle cross member, etc. I probably forgot something.