Not only will you need a T-case, you'll also need a new transmission.
The trans in the truck will not work with any T case without swaping both the tail shaft housing and the output shaft - the 2wd and 4wd version transmission do infact have different output shafts, so it's not a wham bam thing (unless you go custom with something like an atlas....I'm sure it could be made, but thats going to be mega bucks). Additionally, the trans will have to be totally torn down to swap the output shaft....
The next issue is the vehicles computer. While ford did offer some level II rangers with the lever operated transfer cases, other models are electric shift - and given that those lever operated T-cases are fairly new they're going to be expensive as well. Another option would be the older (80's - early 90's) lever operated T-cases, though I'm not sure on their input shafts and the compatibility with a new 4x4 trans. So, if you're going to go electronic shift you'd have to wire all the stuff up for that - including the 4x4 module.
So now you're thinking "I just want to use a damn NP205" right? Wrong - can't be done without a fancy adapter to the 2wd trans. You could swap the whole transmission for something else that's not found in an RBV (ranger/bronco vehicle), but the only way you'll get it to bolt up to the 4.0 is with a fancy adapter....if you check out myers machine over at RRORC I think that he's still making custom mounting plates to adapt any trans to a 4.0 - though I think they only work on OHV 4.0's.....if you're buddy's got an 00' ranger I dont think it's an OHV motor (thought they went out of production in 98, could be wrong though).
So, now you've got to do some research on that issue....do you put a new motor/trans/t-case in it, swap to a 4wd ranger trans/t-case and electrics, or have some fancy adapter made for the trans. Also, keep in mind if this vehicle ever has to be legal/plated in another state that does emissions testing the power train you swap in has to be 2000 or newer (year of the truck and newer).....I'm not sure how those laws apply to transmission swaps, but I'd check into it if he plans to keep it and move out of state.
While it could be done - converting this 2wd to 4wd, it will be very time consuming and could be very expensive. Personally, if it were me I'd start with a 4x4 to begin with, but to each his own.
On to the suspension: If you're running a 9" out back you can chose to run leafs or do a 4 link. But with the front, if you're going to run the 44 with coil springs the easiest set up is to find a C-wedge style axle and use the EB radius arms. Wrist one of them to allow maximum flex. You'll need custom coil buckets, which pottsy over at RRORC makes (guy does awsome fab work - would recommend everything he does). Also, you'll have to consider the track bar/track bar mount. I know with earlier ranger (that have TTB suspension under them) the engine cross member must be modified for clearance - I'm not sure how far the one on the new SLA trucks hangs down, but I'm guessing it's going to have to be modded as well.
If theres one thing I would stress its the fact that you should do lots of research on this before you start if you want to have a nicely built streetable truck. Theres a big difference from doing 10mph on the trail and 80 mph on the highway