It was a little bit of a hassle but I got the upgrade offer and the upgrade.
Delta wanted me to check in before the first flight, which was 3 hours before the LAX-AMS flight that I wanted to upgrade on. Waited with that and when checkin opened went to the KLM website. It would not let me check in with the booking reference and the DL flight number of the SMF-LAX flight, and it did not show any options when I went to "check my trip".
What did work, however, was using the DL booking code and the KL flight number of the LAX-AMS flight. That got me to check in for just that flight, and that's where I saw the upgrade offer. It was $595.47 to upgrade from Y to J, which I took. Not great value, but good enough for me. Sounds like if I had waited until the lounge at LAX that I might have been able to upgrade for less, but I did not want to risk it.
Expertflyer showed J8 and Z7 prior to check-in opening, now just over an hour later it shows J3 and Z2.
Of course my favorite seat on KLM's 747 (1A) was long gone, but it will be my first ride on the upperdeck.
Dennis