I'll do my best:
1) no issues whatsoever...the car/clutch only has 15,000 kms on it...so not a lot of wear to begin with.
2) shifting will depend on whether you're on it or not...but definitely a lot quicker than na with the 3:27s...oddly...with the 4:10s...she doesn't "wander" you have far better control over your speed...you can actually cruise at city limits in 4th and she won't creep up in speed and get you a ticket (like she does with the stock gears). Highway is a breeze in 5th...60 mph she's barely over 2000 rpms...no need to downshift to pass...just squeeze the pedal...and she'll take you right past 150mph right to redline if you want. Bottom line...4:10s make you feel more connected.
3) 4:10s were on before the KB...and I thought the gears woke the car up! The car is just a plain missle with the KB. When you're on it...you've got to shift even quicker than na with the 4:10s...the boost just pulls you to speed even quicker...crusing speeds/rpms don't differ with the KB...but the acceleration sure does...so I'd say there's a need to shift quicker...and a hell of a lot more respect for the go pedal. Grip will be an issue if you slam the gas pedal (1st through 4th!!!!). But at the same time...if you shift between 2-3000 rpms...it's about the easiest car to drive. Mounds of torque low end..so she's real easy to putt around in too. But if you're on a steep uphill slope on a backroad...2800 rpms in 3rd...mash it and she searches for grip...she finds the grip...and by the time you hit the top of the hill...you'd swear you're going airborne.
To put it in perspective...cruising on the highway Saturday with an '03 Mach1, and a '99 GT with 3:73s. From 60mph...the KB GT with 4:10s will effortlessly walk the Mach...it's not even close...and when you look at the stock GT with 3:73s in your mirror...looks like he hit the brakes.
Had a Red GT vert (94-98 model) come flying up on me and our little trio...guessing he was around 90mph while I was doing about 70 mph in 5th (he was coming up quick)...the second he was right beside me...I went down into 4th...mashed it...a few quick seconds go by...I'm shifting into 5th at his rear bumper...and fly by hime like he was standing still...his expression assured me that his neck is still sore today.
More fun than I ever imagined. She's only a toy not a daily driver...and don't plan on taking her down the 1/4...just a real fun toy is all.
For a daily driver...4:10s in a heartbeat...but for a daily driver...I'd think twice about a KB...she guzzles gas now...I like to say she's "20 bucks a ride". She'll actually get good mileage with the KB if you're gentle...but hey..you try and be gentle with this thing! Everytime I've had her out with the KB...I've made a fuel stop.
There's my 2 cents (aka 3 cents Cdn)