Glen,
IM will only sell and fit to an IM[ from an e-mail I sent directly to them], I have been hunting a source for these for a few years. AN old ad in "Excellence" had a vendor in Pasadena, but they are gone.
I was at JPS six years back when I still had my VS, and he stated about $2000.oo with his source.
I love those myself. There is one for sale with them now but not sure the make of the "kit" as it was build years ago.
http://www.classiccars.com/Classifieds/Listing.aspx?data=267D10473CEBE22F8DF777D9763455B3474EF73F024B86DEEB5C5B2E2237EC852A7005C95B7CBC1ACBC6F9F3C8D4FB23&cs=11
Cheers, THOM