I've always thought the same thing. The standard ratio for a C5 Vette with an auto is 2.73 and optional 3.15 and all 6 speed cars (including the Z06) come with 3.42. Being a 280Z is about 500lbs lighter than a Vette (3250 lbs for coupe & 3118 lbs for Z06), going with gears close to OEM would work well, as the factory does goes for be the best "all around" setup. I'll try the 3.36 LSD with the LS6/4L60E combo first and see how it works. Should have enough poo to light them up, anyway.
Of course, tire diameter also comes into play. I bet most have tires shorter than the 275/40-18s or 295/35-18s on back of a Vette, too.