is a track only power adder - not street friendly, and it would be VERY expensive to run on the street anyway. So if you are planning to put it on your car I assume you will be going to the drag strip. Nitrous isn't for a road course, it is a quick power adder for the 1/4 mile so no need to lower the car like someone said - you aren't all that worried about handling in a straight line. The stock driveshaft will be fine too - you won't exceed the tolerance in the 1/4 mile - but the aluminum driveshaft is a good mod anyway.
You will need the 8.8 and tlok, otherwise you won't get the power to the ground, and you will break the 7.5 before long with the torque of the nitrous. Also upgrade the lower control arms on the rear end.
A 75 shot is safe, people have gone to the 100 but when I had it my tuner (Lidio at Alternative Auto) didn't recommend going any higher.
As far as engine mods, the 4.0 can handle it fine - with a proper tune. Brakes will be fine too, no need for different set up there. By the time you get through the traps you will be lifting and coasting and the car will be operating as naturally aspirated so no different than stopping from any speed.
The Zex kit that I had was very easy to install. Get a window switch though - don't rely upon the kit learning wide open throttle, it will fire off very low in the RPM and that is "bad." Set the window switch so it blocks the tach signal from your nitrous controller until you pass at least 2,300 rpm - if you have a stick you want the upper limit set so that when you shift, or miss a shift, you don't over rev too.
Here's some comparison dyno sheets. The torque of nitrous is amazing, I always enjoyed it, just got tired of filling up the bottle every track visit and got a great deal on my supercharger.
With just a C&L and tune
With a 75 shot of nitrous