I agree that the gears are always there.
A new question on that subject, how bad does/will a bottle hurt your motor?
I think an expensive SC would be safer, maybe save your pennies!!??
How do you use the car? I use mine as a daily driver on a 180 mile round trip commute so the gears I want (4:30's) are not an option, I have a ZEX nitrous kit and love it. If I get a bucket to drive daily the gears will be in the Mustang that weekend.
I have about the same commute as you. Now I am driving it everyday to keep the miles of my classics. How often do you have to fill your ZEX tank? What is the cost and how difficult was it to install?