The front diff and springs should bolt in as will the engine crossmember most likely.
The frame width is the same at ~32" but the rear spring perches were wider, and I think the WMS is a bit more. The WMS isn't much of an issue, but you'd need to remove your frame spring perches and mount the square's perches. Most people just bolt new ones on, and that's going to get dangerous when the springs fall off. Also the shocks are staggered on squares so you'll beed to move one frame shock mount at least.
Finally, it looks the the trans crossmember, trans, TC and driveshafts are all missing.
The NP205 is the big boy in stock GM transfer cases, there's also the NP208 and the NP241 is slight improvement over the 208.
Then there's the trans question. Since it bolts to the TC, its a good idea to buy as a pair bolted together. Don't beat on it in low range with an automatic in drive. Its easy to burn them up. You can get a TH350, 700R4, TH400 or 4L60 in automatics. In a manual SM465 or NV4500 are your best bets, but then you need clutch parts, which is a whole discussion.
You also convert to K10 from C20 with that setup.