A quick NICO search...Says the 99-04 wheels wont clear without spacershttp://forums.nicoclub.com/zerothread?id=124940
Pics of 99-04 GT wheels on a S13, but he doesnt say if he's running a spacer.
zerothread?id=137346
98 Cobra wheels; no pics and doesnt say if he's running a spacerhttp://forums.nicoclub.com/zerothread?id=122492
Offset on the 98 Cobra wheels is +31mm (though everyone just says +30). And they were only sold in 98. Thats the only offset I remember off the top of my head, but I have a lot of the specs saved on my PC at home. I'll try to bring them to work tomorrow and add some info.
Nice spreadsheet! I like the way you do your research...