When I did my harness, the P/N is located on the harness about 2 ft from the big connector behind the battery. On a white tag. FYI, it is PN 124 440 2933. This is for EARLY E320 cars.
There is a later harnes PN for E320s. When I worked with Phil at Fastlane, he let me know it is 124 440 56 32.
The harness only differ by some of the connectors installed on each.
Hope the E-mail helps.
1995 E320 Sold at 288kmiles