I have a copy of "Airline Seating Guide, US Edition", published by Carlson Publishing Company, Spring 1992. It has seat maps of all aircraft in an airline's fleet at the time. The seat map for the Delta MD-11 shows 3-4-3 seating, with 12 first class sleeper seats, 52 business class seats, and 250 coach seats. It's also in the Summer 1991 issue.
Apparently it was such an unpopular configuration that they changed it. The Fall 1994 issue shows three different MD-11 configurations for Delta, one with 18-53-164 seats, another with 18-32-215 seats, and another one with 18-32-195 seats, all in a 2-5-2 arrangement. I can't imagine an airline like Delta ordering a 3-4-3 configuration on the MD-11, but apparently they did.
Fly Eastern's Golden Falcon DC-7B