78 Cruise control want to get working
 

Have: Transducer, wiring and vacuum lines. Do not know if transducer works will cross that line later. Vacuum lines are good. Electrical wires check good, but need to power up for sure

Need: I know I need the actuator and mounting bracket. Also need the cruise / blinker switch. Not sure after that.

The transducer has 2 threaded pieces on the back. What connects there? Have been on the Willcox site and have not seen a good diagram. It looks like the speedometer cable goes there??? Not sure.

If anybody has pics of a complete system I would really appreciate the help. Any and all inputs welcome.

First you should purchase the Assembly Manual for your 78.
It will give you great illustrations and part numbers you will need to source parts.
Willcox Corvette offers a .pdf download for troubleshooting LINK:http://repairs.willcoxcorvette.com/w...iagnostics.pdf
78-Early 79 used the same Servo, Bracket and Rod & Link.
The photo below is the correct Servo, Servo Rod, and Bracket for your car.
Servo GM #6466530
Servo Rod and Link, Rod GM #468238 and Link GM #376197
I don't have the GM Bracket part number.
https://cimg7.ibsrv.net/gimg/www.cor...b5c6375a6d.jpg
Servo Front Side Photo:
https://cimg5.ibsrv.net/gimg/www.cor...f17651c380.jpg
78-Early 79 Servo Rod & Link:
The Late 79 Rod length is different, something to watch for.
https://cimg8.ibsrv.net/gimg/www.cor...8bb0a33d31.jpg

Here is the Servo mounting Bracket Setup for your 78.
EBAY LINK:https://www.ebay.com/itm/14399853591...EAAOSwjv9galqC

The two "screw threads" are for the speedometer cable IN (from transmission) and speedometer cable OUT (to speedo) which provide the speed signal for the transducer.
BEFORE you throw money at replacing the transducer assembly, you need to check out ALL electrical wires involved with the system (brake switch connection; power and ground to transducer; ON/OFF/ACCEL/RESUME switch and association wiring) to make certain they are NOT the cause of your issues. Also check the fuse for the Cruise system.

If you need to replace your transducer and purchase other components, you may wish to make a choice between getting the stock system up and running, OR just replacing the old vacuum-style cruise control system with a modern all-electronic system (Rostra). If you purchase the Rostra system, your turn-signal lever cruise switch will operate it with no problem. You just need to make proper connections at the end of the wire coming out of the steering column (base).

I have a Holley Sniper EFI that has a transmission controller that has its own connections using the speedo cable. Was doing some research and think that the original system will not work with my setup because of the transducer. Will look into the Rostra system. Thanks for the input.

Should probably elaborate some more. I have a 700R4 overdrive transmission in the car. The speedo connection i referred to is for the transmission. It took a bit of time to get Sniper EFI and transmission dialed in so they would work together. Looking at other forums about the cruise control is where the transducer issue came up.