There are a few downsides to the Quaife or Wavetrac in a Viper or other high HP rear wheel drive car on a road course or track. The torque biasing can get screwed up over time with heat and lack of maintenance. This can and has caused the inside tire to spin in high speed turns when hot and after some track time, so make sure and change your fluid often and have it rebuilt at 10K miles or less if you track your car regularly.
Both are great for the street and light track duty as they help keep the car straight when accelerating hard in a straight line.
On the gear ratio, the 3.07's work best for most on the track but this depends somewhat on what tracks you drive regularly. With a lower gear, i.e. higher numerically, you will be shifting more often on the track and every shift is time you are not accelerating.
If you take a close look at the Gen V gear ratios, SRT went to a 3.55 rear gear but changed the transmission gear ratios to give us about the same overall gear / speed out of each of the first three gears, while 4th is a bit shorter.
Good luck,
Dan