My recollection from this past summer is I called Delta Res and asked them to find the KL record locator. (I believe both KL/AF use the same record locator but not DL.) The woman at DL Res took awhile to find it, struggling and then suddenly saying, "Oh, I think I found it." She might have had to go into Delta's old system to locate it but I'm not sure. When I went over to KL's system, the number she gave me worked and I was able to select seats.