I have a GV OD on my hardtop Challenger. I'm quite pleased with it (Rear ratio is 3.55).
A little more highway RPM than I had with the Tremec 5-speed that was there before (which had a .64 final ratio), but still very useable (2800 RPM vs. 2400 RPM).
Had to hammer the tunnel floor a bit, have a custom shaft made, but other than that, pretty straightforward (I actually had CRT build the trans with the OD).
A little bit of electrical work too, since the Gear Vendors control box looks like it was designed by a 5-year old (4 sides to the box, with connectors on three sides, and the connectors used are a bit surprising for the price range...)

When time came to plan the rebuild of my convertible though, I found (here on Moparts) a 2.94 pumpkin to replace my 3.23 gears, and I'll stick with a standard 3-speed 727. With a swift, high-revving 383 and a 2500 RPM torque converter, that ought to be more than enough for a fun car.
Of course, that's my opinion since "my toy car has a roof", and I chose to simply match the taller gears with a looser-than-stock converter. I won't be racing the convertible.