Where do you race? See what most are racing. Check your LHS to see what parts are stocked.
I bought one of the first ZX-5's in the Houston area (2-2005). Until just recently, I had to be my own stocking dealer. We now have about 5-6 racing every week. The LHS has 2 of most everything now. Much easier!
Do your homework, you will be much happier.