I just ran across this crank fire set up for the 911 (no, I'm not the seller):
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=38656&item=7954785673&rd=1&ssPageName=WDVW
Seems to me that you could set up the low voltage sender to be wired to two MSD ignitions and coils and drive dual plugs that way. Since it is just a sending unit, it should be a snap. Am I completely over simplifying this?
This setup would be far cheaper than a 964 or RSR setup if you bought all of the MSD components used. They are a dime a dozen from the Detroit crowd on Ebay...