From what I heard GV only wants to deal with people that buy from them. So if you buy used and need parts you are screwed. Think you need to dimple the floor board to make it fit.
This is not true. They have been totally cool to me and I bought mine used from a pal that decided to switch to a 6 speed trans.
You will NOT get a 36 % drop in RPMs.
If you are travelling at 3200 RPMS, the 22% reduction in overdrive will get you down to about 2500. The OD is .78.
My Charger has a 727 with the GV Overdrive and a 3.91 axle. This puts me at 3.05 in OD. I don't know what mods are required with a Dart, but I'd bet that they are more extensive than with the larger B body tunnel. I had to dimple the trans tunnel at 10:30 and 1:30 to clear two bolts on the GV unit.
I am quite happy with mine. It upshifts just like a tight 727. I have taked 2 1000 mile trips with it and got 12.8 mpg with an engine that is far from optimized for economy. I got 11.3 with a 3.23 and NO overdrive the year before. Now I have great acceleration and better highway manners. I'd like it if the OD ratio were .69 or .70, but the .78 is the only ratio offered.
