I've seen them on Summit... and they're not cheap. I have a manual, but I'm interested in the responses here.
I have 2 Dakota Digital units made by Rostra. They both work well. You may have to glue magnets to your driveshaft. Don't know if the have a pulse generator for C4. I had to do that on my 61 Buick. Works fine.
Dakota Digital (Rostra) work well. Programming is sometimes a bit of a challenge, but they work very well.
The Rostra 250-1223 Universal Electronic Cruise Control is truly universal and requires no vacuum connection. I was going to use it on one of my bikes but fixed my old Audiovox vacuum operated one instead. https://tinyurl.com/ycyhetvs
I am a bit o a dinosaur I guess. I still go to the salvage yards. I found one from a 1994 Caprice that is seeing duty on my 1950 Buick. Ben
I have a Dakota digital on my 49 Buick. Needed to screw on a pulse generator onto the 400 transmission, then the speedometer cable. It all came with the kit and works great. I would buy another, and probably will for my 56 T-Bird this winter.