You're 2wd and don't even have a Tcase. I nissan case wont bolt up to your transmission; you'd need a 4x4 transmission to do that.

Another option is finding a divorced case you could mount in a custom cradle behind your transmission, and use a short shaft from the trans output into the case. Toyota cases can be converted to divorced with a kit for passenger side front driveshaft output. Dana 300s can be used for a driver side output. All this wlll require fabrication of a case mount, shifter, and new driveshafts.

Depending on what case you choose, you'll need to select an axle - really 2 axles, as your rear H190 is a boat anchor that's not well suited for a 4x4 due to its lack of gearing and traction device possibilities, and the fact it's just tiny. You'll want to upgrade the rear to at least a 4x4 Nissan axle, but a rear Toyota axle, or 86-91 full size jeep wagoneer Dana 44, or a rear Isuzu Rodeo Dana 44 are all good choices that can be built up for a lot less money than a Nissan axle. Cutting and rewelding of spring perches, shock mounts, etc. will be necessary here

On the front, the cheapest/easiest setup is a leaf spring SAS. Calmini makes several parts to make this easier, such as a spring hanger, shackles, etc. but you're still going to need to fab steering, shock mounts, as well as do the welding for the hanger, cut holes in the frame and weld the shackle mounts, etc. It's a fair amount of work, and it has to be done right. If you get things in there a little crooked, the truck won't be drivable on the road.

If you're thinking of having a fab shop do all this, figure on at least 10 grand. If you do EVERYTHING yourself, you could probably get something done for $3-4k if you really go the cheap on everything. It's not a project for a novice.