On the drivers side frame, near the slave cylinder, are some threaded holes used, I believe, for the Alpine trans mount. If there is no cable at all, just buy the proper length cable (About the same gauge as the battery cables) with the proper connectors so you can bolt it to the frame and one of the bell housing bolts or slave cylinder bracket. You will need to scrape or sand the surface on the frame to make sure you get a good connection. If the bell housing and/or slave cylinder bracket are not painted, you should just be able to clean the surface and be hot to go.
If you think about it, the engine’s only attachment to the car is via rubber mounts. The cable is necessary for a good engine ground.
Happy Motoring