If your motor still has stock heads and cams, 4.30's will be a little too much gear for 26" tires. I run 4.10's with 275/40/17 DR and they are just under 26" tall. I cross the line at 53-5500rpm.
If you are shifting at 6000rpm or more, then the 4.30's might be alright with you setup. I know a couple of guys with Mach 1's and they run 4.30's, but they redline at, I think 6700-6800rpm.
Is your car an automatic or a stick ? I figured I would ask because no one else has asked, and you enver specified which you have. Also, since you have aftermarket cams, where is your rev-limiter set at, and at what rpm do you shift at ?
I have 4.30 gears in my 01 GT and mine is an automatic. To be honest, I love them. Sure, the highway rpms can get a bit high once you start going above 70mph, but I love how fast they let you accelerate, and climb through each gear. Works great in town.