Stano,
I added "factory" cruise to a '70 conv. It was too easy. My wife and I went through a bunch of 70s Chevys at a salvage yard and removed more than enough parts to make a factory installation.
You will need:
1. Transducer (this is what makes the cruise work) with the speedo cable that goes to the tranny.
2. ALL the vacuum hoses and connectors for the transducer/servo/brake pedal.
3. Servo (this is the vacuum pod that actuates the throttle). The '69 would normally use a servo mounted to the left inner fender beside the transducer, but I used one that mounts to the rear of the left head which makes a neater installation.
4. Linkage between throttle (don't forget the ball stud on carb) and servo. Depending on whether the car was 2/4bl, the linkages are different length. So grab 2 or 3 different ones.
5. Wiring harness. Be sure to carefully UNPLUG all connections and remove it from where it goes through the firewall.
6. Vacuum and elec switches and the round retaining clips attached to bracket for brake pedal. This bracket (as far as I know) is factory installed on all cars, including yours. So you won't need to get this bracket.
7. Last, but not least, the trun signal lever with cruise switch. You may or may not be able to find a good one. If not you can buy a new one.
As I remember, most of my cruise components came off of mid 70s MCs and big Chevys.
When I got mine installed it worked perfect the first time. You may get lucky and get a good transducer. If not, just to be safe you might get 3-4, or they are available rebuilt with an exchange. (no longer new)
It took some time to neatly install all these components to make it look like Chev did it at the factory. The most difficult part was threading the wire for the turn signal lever down the column (use a long, thin piece of wire attached to the wire to pull it through). But now that is is installed, it was worth the effort.
One last thought. You might check the ads here at TC for a cruise system.
------------------
Tom Parsons