RE: blowup of a AMC 20 rear end
Can you do it? Yes. It's fairly easy with aftermarket kits and parts. A conversion using later factory stuff is pretty slick too.
Price? All over the board. I've never converted one, so I'm no help here. Kit prices are available in most catalogs and on the net.
Is it worth it? Depends. FI is more economical from a mileage standpoint, doesn't need to be manually adjusted for different conditions, gives better throttle response in a broader range, and handles angles ALOT better. Carbs are easier to adjust over a broader range(yes they ARE), cheaper to setup, and they make just as much power at WOT as FI.
I'd do it if the budget allows. A properly operating carb does good enough though that I would concentrate on getting all of your other mods done first unless you absolutely have to have FI for what you're doing.