You are in a dilemma: You want IFS, but don't want to chop a good original frame for IFS. You're considering a chassis swap, but you're not a welder and that entails lots of fabrication. Plus you said you don't have many years left - both strategies take time.
I guess you could always buy an Art Morrison or Roadster Shop chassis. They're expensive, but they're what the pro shops all use to get projects done in a few weeks. They're custom-made for your year, make and model truck. You just paint 'em and assemble the truck like a big model car kit. There's also a guy on Ebay who'll build your truck to your specs; last I saw he was charging about $20K depending on how you want it equipped.
My advice: Don't get in over your head by trying to build two trucks at once. Build the first truck on an original frame and original suspension (all refurbished of course) as you planned. You can add disc brakes and dropped axle for stopping power and a cool stance. Enjoy the heck out of it for a few years, then if you feel like doing the second cab you can always do it later.
