You are talking about racing discs. Bonneville salt flat racing discs. Volumes have been written on the subject. Best prices I have found are in: Go-Kat-Go
Go here for a lot of discussion on them:
http://www.gassavers.org/archive/ind...ps/t-1539.html
They also list a place that has them for $38 for 4 or something.
I have them on my Geo and I am presently in the process of screwing them on with stainless steel screws....I lost one, had to buy another of the snap fit ones. They really enhance the look and the FE.