2wd to 4wd conversion - 68 GMC Stepside

[68 GMC Stepside]

I have a 68 GMC stepside 1/2 ton, 2wd, 250, 4 speed manual. Have been researching swapping out the front end to upgrade to disc brakes. Have also considered upgrading suspension to 3/4 ton. Am now thinking why not swap out front end, suspension, diff, transfer case etc and wind up with disc brakes, 3/4 ton suspension and 4wd. Does anyone know if it is as simple as finding a donor 3/4 ton 4wd and swapping everything? If that will work, what components need to be swapped and what year of trucks will be compatable? I'm assuming a new rear driveshaft would be in order due to length as well. Thanks in advance.