Hmmmm...I'm going to assume that you mean going from carb to Fuel Injection options first of all...yes, it is an option but you need to change the entire wiring harness, possibly including the interior harness since the systems are different at the firewall. As well you would need the intake and TB, as well as an in-tank low pressure fuel pump and a frame-rail high pressure fuel pump.
For this you would need a donar vehicle or a good junkyard...unless you want to spend 400-700 on a wiring harness from Ford and then add up all the other required parts.
Since the wiring and setup of a carbed engine (one or two bbl?) is relatively simple you may be better off considering staying with the carb.
As far as a high idle, that can be caused by a number of things...including a vacuum leak, adjustments on the carb itself (again, one or two bbl?) or a idle control solenoid that has gone bad or not connected properly. You can also adjust the idle simply by turning the distributor a few degrees (clockwise usually lowers the idle on mine) where the timing is slightly altered.