Yeah this thing was around in the late 60' early 70's. I put one in a Nova 4sp with a big block and and another in a Ford van with a manual and a custom made Hurst linkage. The Nova I don't think ever got rid of the drive line vibration. I think the car itself was flexing as at the time body stiffening was not real common. The motor was pretty strong for the day. It never broke but it always had a shake at some speed. The car eventually was trailered and made even more raqce car only.

The van on the other hand worked great. I don't remember what gear we put in the rear end but it was around a 4.56 as the guy pulled a big trailer with it. He wanted something to get better mileage when not towing yet had good gear control when towing. The thing shifted great and the special linkage worked very well. You could split shift it nicely with a little practice.

I think they were just too expensive and required extensive modifications to install that the average guy just didn't have access to back then.