Based on the description, I am assuming you have been talking to M&A Castings. Fran Kress uses them for a variety of wheels including GT40 MKII, GT40 MkIV and FIA. I believe Kidney Beans are in the works which I am personally interested in for my '63 Comp Car replica. He may have SC wheels available as well.
His contact info is at
http://www.cobracountry.com/kress . You will find that his prices are very high -- significantly higher than what you are quoting.