You can use your stock wiring harness and modify it. You'll have to get a 99+ gs-r ecm or do some ecm pigtail swapping. And if you're going to do that, might as well go obdI. As for the mounts, you'll need the 99+ Si driver's upper bracket (bolt's to block) and 99+ Si rear tranny bracket. After that, you use the B brackets and D mounts. Hope this helps.