Buy another 1996 Ranger the same body style as yours but with 4wd.
Sell what you don't need, clean up the frame, swap body parts over.
Converting is a neat idea, but when you really get down to swapping parts on/off of the frames, it's just too much work and way too much can be done incorrectly resulting in you getting seriously injured/dying or someone else getting seriously injured /dying. The stock route that is, it's actually quite involved.
It is easier to use a solid axle up front, but you need a lot of lift to accomplish this, at the LEAST 4-5" over stock.
Unless you know exactly what you're doing, swap the frames. You'll end up with a plenty nice product if you clean it up good. And you'll be able to drive your truck in the mean time.
As for the diesel swap, that's a whole 'nother ball game, and one I don't have the time to type out (again) at this juncture in time.