Is it possible....
 

... to swap 18" rims on the sports package Z? Will it fit the huge 14" brakes? I want to get track dedicated rims and tyres as it's more cost efficient, and there are more options of tyres to choose from.

Possible?

I've been told that it is possible and that the rim will clear the calipers in most cases. However no one has told me which particular wheels will fit just yet. I'm in the same boat as you.

^^^+1

Most 18s will fit, some will not. It depends on the inner hoop diameter. I test fit the 18s off of my time attack 350Z when I first got the 370Z. The fronts fit, the rears didn't. The spokes cleared fine, but the calipers was rubbing ever so slightly on the inner barrell of the wheel. Nothing a little grinding on the caliper wouldn't fix though :).

http://www.the370z.com/members/ddmot...-toyo-r888.jpg