There's a variety of options out there, depending on how much you want to spend, or how much you want to tune.

You can go from EZ-EFI for a chunk of change, but it self tunes. Or you can go with Megasquirt for a few hundred, but you have to tune it yourself. There's also the Ford EFI system some of us are working on that should be cheap and fairly well tuned already.

Basically, the more plug and play it is, the more it will cost.