I was fortunate that my car was in a state of disassembly because i'm not sure I would have taken the time to install the CC had it not been apart. No fenders on the car, and I had the dash off. Because of that fact, it was very easy to add factory OEM cruise control to my non-cruise '88.
The pedal assembles are different in the sense that the mounts for the brake vac switch and the clutch cancel switch bolt to the pedal assembly and are not present on the non-cruise assemblies. They can be added, but you need to be very flexible if you intend on getting them on a pedal assembly with the dash in place. you will swear a lot.
I put together a thread on what I found during my research in terms of parts, part numbers, wiring diagrams, and some diagnostic info. When I was searching for this, I found very little info, other than the typical "Throw that in the trash" comments, especially on Bookface.
Pertains mostly to the 87-93 cars, but I think 84-86 is the same.
Done a little research into this and figured what I learned should be put into a thread and added to the tech sticky. As you can imagine, nobody really gives much thought to cruise control on these cars, so many searched threads had dead ends. So many this will help someone out down the road...
www.stangnet.com
Since this thread is likely to get searched for and bumped again, some more info won't hurt.