This questions been asked before and this is what I said to nissanman...
That's the thing though ~ do you just want a fast car or do you want the Zed to be a faster car?
If it's the former then just sell up & buy a different car, ..but if it's the latter then you know it's not going to be cheap but you will have a more unique faster Zed afterwards.
I decided to supercharge my Zed as I have always wanted to drive and experience a supercharged car plus I love the looks of the 350. Personally I don't think there are many cars which lend themselves to being supercharged quite as well as the 350/370 Z do.
I had considered doing it in the past to my old EP3 Civic Type R but with it's fwd layout I just knew it wouldn't handle the power as well & I'd probably ruin it's handling overall.
As you've already owned a few Zeds Luke either it's time to try something new or maybe it's time to take your current Zed to the next level but at the end of the day it's your decision & you're the one that has to live with it so take your time deciding.
Good luck.