Dave, try corral and buckeye stangs I always see them, also look on ebay there is a company that sells them buy it now or get the jegs brand, I just picked up a gt 40 intake and will be going with a 1/2 once do the inch ones clear stock hoods? not sure might want to check.
http://cgi.ebay.com/ebaymotors/GT40-5-0-FORD-MUSTANG-EXPLORER-INTAKE-MANIFOLD-SPACER_W0QQcmdZViewItemQQcategoryZ38634QQihZ022QQitemZ350060739837QQrdZ1QQsspagenameZWDVW