What in HECK was that old overdrive called

NO...........The unit I am thinking of looked just like a sawed off A833, and bolted to the FRONT of the main gearbox. It would have functioned just like a 4th gear (straight through) and 3rd gear overdrive, just like the Mopar OD 4 speed

As I say, it may have been short lived. This was a "long time ago"