Another source you can use in addition to Lois is Kevin Marti, Kevin has a web site called Marti Auto Works (I think!) Also, in the April 2001 issue of Mustang Monthly is a related article on Kevin's capabilities. (page16) Good Luck!
Lois has the invoice for 69-73 Dearborn Mustangs and 70 Metuchen Mustangs only. She charges $35 for non-Boss and $40 for Boss invoices. Mail a check with proof of ownership to:
Dearborn, MI 48121