First question. Did that 84 originally come with a EFI set-up? If so, does it now currently have a carburetor on it? If so, then without some pretty serious upgrades, the 600 CFM carb is too much for that 302. If it is currently an EFI computer controlled system, then you need to do some fairly serious alterations.
The '83-early '85 EFI cars have 2 fuel pumps... A frame mounted high PSI unit, and a 6 PSI in-tank pump. If you remove the frame pump, and replace it with a chunk of rubber fuel line, you will have the right set-up for a carb, plus have the room to convert to the '86-up true dual exhaust.
As far as the rest goes, you will need a carb syle Duraspark distributer and ignition box, which you can rob from any '74-'84 carbed' 302. ('85 Carbed Mustang dizzy's have a steel gear for the roller cam, which you can't use)
You can also ditch the EEC and all the EFI related wiring.