You're trying to reinvent the wheel twice here. RHD 164 used the cable clutch. It's untidy as it has a long route across the engine. Cable clutch came in with the B20 cars and then the B30. Vacuum for brakes should be fine if everything is in good order. Don't know anything about "hydro boost" but diesel cars use an electric vacuum pump so that might be worth looking at if you want to experiment. As said though the original set-up works fine.