I have honestly always had good luck with less gear, especially street racing. On the street, the car that makes mph is going to win. My old mustang ran 6.70 @ 102 in the 1/8 with a 3.73 gear, and a c-4. I had an '87 hatchback with a 5 speed, only mods were off road h-pipe, mufflers, turndowns, pulley, and a dry kit with the biggest jets I could find. Ran a 11.99 in the 1/4 with a 7.6 1/8 then went a 7.5 two weeks later at sunshine, the car had a 2.73 gear!! My roadmaster now only has a 3.08 with a th350 trans, and my 60' is 1.72 so far. Honestly, people like to rate nitrous kits by the horsepower because that is what everybody wants to hear, you should really think of it as torque in a bottle. Hit the kit in high gear, hardly anything happens, it makes it's power down low, that's why I would say stick with a lower gear. I'm not even sure I'd go 3.73, maybe 3.42? Definately not your 4.10's, you are just going to blow the freakin' tires off, and once you hook, you'll be out of gear.