That roof cancer is kind of bad......but nothing that can't be fixed. Looks like someone got really carried away with installing a stereo
Again that can be fixed too. They sell a patch panel for that for about $50.00.
That rear differential is a 12 bolt, same as the C10's came with. The blocks in the rear are original. I have to agree the transfer case looks to be a Rockwell T-221. Not the best transfer case but should be fine as long as you don't let the oil level get low. Low oil level will kill one in a hurry. And yes a closed knuckle Dana 44 in the front
4X Burbs are really cool. I used to have a '63 4X burb.....wish I hadn't sold it. I've got one to build though......someday.
Keep us posted on your progress.