Gear vendors OD

If you are just curious about what gears make a decent combination, I have a few observations.
I have a buddy that had a '71 Challenger. He ran a 416 with a 727. 4.56 gears and the Gear Vendors. Even in OD, it was still a gas hog. It was only raced a few times. He is a great guy but makes some bad decisions with cars. He later swapped in a Tremec 5 speed and switched to 3.91 gears.
I bought the GV unit and had it in my Charger with a 440/493 and 4.10 gears. I later switched to 3.91s with it. The 3.91s in OD were just over 3.05 give or take. Not bad at freeway speeds but the unit I had wasn't ideal. It was an early unit that had no mount for the floor shifter. An add on bracket had to be used. This resulted in sloppy shifter feel and the occasional habit of the trans NOT staying in PARK....W T F ?? Yeah, the car would start to roll and I'd be walking away....Huh?? Turn back and get in the car to smack the shifter a few times to get it to lock in. Also, the OD would sometimes NOT disengage as I slowed to a stop. Yeah....I'd end up leaving a stop in 1st OD and 2nd OD. THis was annoying.