I have a 87 iroc with iroc wheels what size lug nuts do i need an do i use washers. i have some but dont know if they are the right ones send pic. if any Thanks.

The lugs thread pitch has gotta be, 12x1.5

I don't think it matters much if you use an open ended lug nut or a closed end? I had open ended lugs on my stock RS wheels, but now have closed end locking lugs on my Z06 wheels. You don't use any washers.