edit: darn. some people beat me to some of the stuff i was sayin while i was typin. oh well, too lazy to delete it.
as for gains, i heard that for every 100lbs you reduce from the car you gain about .10 of a second ET on the 1/4mile. it’s a pretty sketchy rule though. for lighter cars i’m pretty sure its a little more than .10 of a second. For daily driving, there isnt much yet for this car that would reduce weight other than a good set of rims. of course, the hood can be replaced with carbon fiber. i’m not sure about the specs of the Fairlady Z but some JDM parts are lighter than USDM parts. for example, Honda made lighter control arms (around 3lbs/each) and sway bars for the Japanese Integra type R. Again, Im not sure if it’s the same case with Nissan. and there are also lighter aftermarket AC compressors out there but i dunno how reliable those are. Oh, some people who take their daily drivers to the track remove carpeting (i’d say around 10-20lbs) and spare tire (since it’s a full size, i guess 30-40lbs). good luck when you get a flat though.