Pace Maker Yachts

I am looking for some information regarding a stretched 65' Pace Maker. The vessel was built in 1979, and I don't have any information regarding the date of the modification, there was 15' added to the length at the stern for an 80' LOA , and I was told that there were 8 of these vessels that were done. I am trying to redocument the vessel and I need to find out who did the modification so that I can get the specifications from the yard that did the work so that I can submit them to the USCG. Any information that could be provided would be greatly appreciated. Thanks