Welcome, Attic Man!
I don't know...mine are still on their way. If you've already done a comprehensive search, then you probably know more than me already. Lots of options for this one depending on what you've already got at your disposal. Many discrete op-amps have been made available through tech talk and friends of tech talk, and there are lots of options available to you. Do you have input transformers yet? They do make a difference on your selection of op-amp; anything with a FET input and you could have up to a 1:10 input transformer, whereas if you go with the John Hardy 990 I think the ideal would be more like a 1:2 (that's from memory, and probably wrong).
I've already got plenty of Sowter 1:7 input trannys and 8 output trannies on their way. I'm probably going to fit these into an 8-way rack that I've got left over from a previous project. I think I'll modify it in such a way that the power rails will carry phantom and something like +-30V or so (unregulated), allowing individual preamp cards the choice of whatever voltage they like to see, with local regulators. That's just one idea (non-purist) for this project, and I think you'll find there's lots more floating about!
Anyway, if you're really after an API clone, then you will need someone more well versed in their history than I...good luck!