4.56 + N2o?
 

I'm considering the prospect of a 4.56 rear with 275/40/17 DRs and about a 100-125 shot of N2O on my 98 Cobra. Is this too much power for the tires? Would I run out of gear at the end of the 1/4? I don't want a slick but I would be willing to step down to a 4.30 if that's what it takes.

I'd probably go with the 4.30's. This combo should work with drag radials just don't use the nitrous on the launch. I like the the BF Goodrich Comp T/A drag radials. They hook up quite well.

Is this going to be a street car?

If so, I'd go with 4.10s...

This will be a street car that sees limited miles. Just weekends and maybe the farthest I'd drive is 25 miles one way. 4.56s just seem so cool. :D

I have a 97 Mustang GT. I have the 4.10 gears with a 150 shot of Nitrous on it. The cars best ET is 12.42 at 108 mph. I drive the car everday and I love the 4.10 gears. If I did not have to drive it everday I would have maybe gone with a 4.30 gear. I have run the car with slicks and the car has not had any problems. I have run may passes with the car. I baught the MSD DIS 4 ignition, its really good. Lets you retard the timing differently at different rpms and has a rev limit you can set. Good if you want to run NOS. Good luck!