Fieros are mid 80's technology and still used a vacuum based cruise control setup. As people install later model engines, many have started to upgrade the cruise technology. In the late 90's and early 2000's, GM switched to a digital cruise control modules on most of their cars and trucks. These modules are essentially self contained with a cable for the throttle body and about 10 wires to hook up.
These modules also come with a removable cable, and many available cable lengths. So its just a matter of finding the right cable that will work with your application.
From a wiring stand point, they are very simple. Ground, 12V power, inputs from GM Cruise stalk, brake/clutch inputs, and a 4K ppm VSS signal. So as long as your ECM has a 4K ppm output, you can use one of these modules for cruise control in your GM car. The only tricky parts with the wiring are the two brake switch inputs to the cruise module. These are opposite of each other, and the inputs must switch from ground to 12v and 12v to ground, at the same time, as the brake or clutch pedal is pressed. To accomplish this for a manual transmission application, I wired the brake and clutch switches in series and used two 5-pin relays to swap the input signals from ground to 12V. See wiring diagram below.
The 2007 LS4 in my 88 Fiero is a Drive By Wire (DBW) setup and uses the E67 ECM. In the stock configuration, the LS4 E67 routes the cruise control through the Body Control Module (BCM) and through the High Speed GM LAN (CAN) wires. Since I didn't install the BCM when I did my swap, I had to come up with a different method for cruise control.
Since the LS4 doesn't have a cable operated throttle body on the engine, I decided to use the AR Cruise Module and its cable to activate the DBW pedal. To do this I made some brackets that either welded or bolted to the pedal assembly that would accept the end of the AR cruise module cable. I also took out the dash so I could mount the module up under the dash and by the HVAC unit.
The only connection the AR Cruise Module needed to the E67 ECM is for the VSS signal wire to be connected to (C1-Blue, Pin 39). This is the VSS output pin for the TBSS and CTSV, but is also works with the LS4 E67 calibration.