I converted my '68 coupe (originally a 302/C4 car) into EFI with a T-5 a little over 2 years ago. When I did the swap I used a Ford Motorsport 5.0 crate motor and a new Tremec T-5. I chose to use the Windsor Fox wiring harness and trans. crossmember. It was a pretty easy install, I only had to splice a few wires into the original harness and there aren't too many "extra wires" laying around.
As for clutch specifics, I originally used the old mechanical linkage from a junkyard car. I had purchased JBA shorty headers but I couldn't get them to clear the mechanical linkage so I used long tube headers instead. I drove the car with the mechanical linkage set up for almost two years (hating it the entire time) learning to live with the clutch chatter and squeaky sounds, until the clutch rod snapped on me in traffic. After that experience I chose to use a hydraulic clutch set up from CJ Pony Parts, the difference was like night and day, now the clutch feel and peformance is like a late model Mustang. I would have liked to use a cable clutch, but I did not have time to fabricate the brackets needed for the conversion (this car is my daily driver). Now with the hydraulic clutch I use the JBA shorty headers, it makes negotiating speed bumps much easier.
I put somewhere around 16,000 miles on my car a year, I average 22mpg highway and I just ran my car on a "Mustang" chassis dyno to a (very traction limited) 13.94 et. at 102.1mph. The advantages of EFI in old Mustangs like ours are great. I have a reasonable amount of experience with tunning and working with EFI now, so if you run into trouble with your install I would be glad to help.
Also, I did my conversion when I was 22 and I had a very limited budget as well. You just have to keep in mind that sometimes you have to spend a little to get the quality you desire.
Good Luck
