I have spent more time, money, and effort on my IFS than I care to admit. I think most here think I am a bit nuts and quite stupid for doing so, but I enjoy a challenge and like to try things off the beaten path.
A couple of things I can tell you:
You have an old vehicle, with old components. If you do decide to lift it, add in the cost of replacement ball joints, tie rods, tie rod ends, and maybe some idler arm bushings.
A skinny 33" tire is best for these suspensions. They are robust, but you MUST understand how to drive them. They are a factory system, and have their weaknesses: if you learn them, you will be okay. I'm happy to discuss with you my experiences sometime if you wish.
All that being said, if you plan to run this truck fairly hard off road, and/or like big tires, you should do the SAS. Running IFS hard requires more maintenance, and patience, than most sane people have. (I wouldn't consider myself particularly sane at this point).
Many in this club run SAS runners and trucks, and I have heard VERY good things about them.
Couple of things I'll point out:
1. A traditional leaf spring swap is somewhat high for short statured folks; kids, for an example. In order to clear the steering, you need ~3" of lift. If you plan on DDing/running kids around, keep that in mind. You may have to do a bit of lifting.
2. The cost up front is a bit intimidating. However, consider that I've spent easily that on my IFS over time, likely more. The cost will get you either way.
3. For moderate trail running, DDing, and camping duties, the IFS will serve VERY well. Keep the front suspension in relatively stock form, and you will be just fine. Remember, a 33x10.5" tire on a stock back spaced rim will fit in the front of these trucks by simply folding the pinch weld over. Ball joint spacers provide lift, but do not restrict travel, and thus you cannot fit any bigger tire under the truck, as the suspension and wheel compress to the very same spot regardless.
4. I have a biased opinion, but its how I did it, so take that with a grain of salt: I always advocate running the truck stock with a good set of stock sized tires for 2 or 3 years. Stock form forces you to rely soley on your wits. It can be a bit frazzling, but you will be glad of it later. I drove my truck for 4 years before doing anything to it. It did have steel bumpers but those were due to accident replacements before it was mine.
Other than that, I'm happy to discuss the ins and outs of IFS with you any time. I've mutated mine enough that I can at least give you a list of things NOT to do!
Cheers, and welcome!