I know what Z you are talking about in the January 2008 issue. The red one with the G-nose air dam and the really wide rounded fenders that are gray, right? I don't think that is what he is after.
zr240 do you want the really aerodynamic rear fenders that most Super GT cars have? And the front fenders that have the large trailing vent behind the front wheels? How hard core racing are you going? This way I can gage how to design the kit. I could sketch something up. You are planning on going wide body, right?
Do you want: Full wide body kit (front fascia, front fenders, side skirts, rear fascia, rear diffuser, front splitter, large "GT" wing, vented hood, front bumper canards, JDM style fender mirrors. You mentioned G-nose style front so I know that detail for certain.
Would you like it to be NISMO inspired (take some design cues from the current GT300/500 Z-cars)?
Fill me in on these details and I can sketch up something that will give you some ideas.