I Duraspark swapped several 2.8s years ago...easy process on 83/84, 85 is slightly different. One little quirk I ran into with the Duraspark coil was that I had to add a ballast resistor, that coil only need like 8v and a full 12v from your battery will overheat it. That's the nice thing about using a GM HEI module and your TFI coil, you don't need to buy all that crap...just the HEI module and some wire.
If you can find a good junkyard carb, that would be ideal... preferable over a Chinese one... but either will work. The carb you have now can be used, if I remember right you have to build a metering block for it though, similar to this:
http://www.cardomain.com/ridepost/3816516/1986-ford-ranger-regular-cab/
One other thing, if you look for distributors for say a '78 Mustang II, there are three options: single vacuum, double vacuum, or Bosch. You don't really want the Bosch one, it uses a funky cap and the wires to fit it are kinda hard to find as well.