The 4.013 rear end is going to be one of hell of a switch from your current 3.5. I think thats the Titan rear end correct? Only person that will install that for you is going to be Performance Factory. That rear is a bitch to get in the Z. I would suggest the 3.9 ESPECIALLY if you daily drive your Z.

The JWT flywheel is a major improvement acceleration wise vs our stock set up. As you've probably heard that the JWT is the noisiest swap out of the bunch. They were not lien. Gears will be very clunky when the car is cold. Slightly notchier at lower RPMS, but an overall improvement. Clutch pedal feels about the same stifness, but the catch point will be lower than your stock clutch.

Buddy Club Coilovers
Hotchkis Sways(3 point adjustable type)
Camber(Brand?)(needed?)

your suspension upgrades are where its at. Hotchkis sways kick ass, but can you still find them?

Buddy Club coilovers get down with it, i personally dont have any experence but have heard good things.

Camber will be needed depending on what offsets you are running with your rim set up. I'm in Largo/Clearwater bolted up to the fullest. Hit me up sometime.