This might be a dumb question, but I believe that the current wheel manufacturers like PSE, Vintage, Trigo, etc. only do aluminum reproductions of the original magnesium wheel. I haven't found anyone that makes a true magnesium wheel for these cars and am curious as to why.
I understand that they would cost more, but their weight is I believe 35-40% less than aluminum. We used them on the Indy Lights car and they were very light and could take a pretty good whack (don't ask how I know). Maintenance of them was no more than aluminum.
Edit- Just found these guys-
http://www.macastings.com/products.html
Who sells their wheels?