Sorry, I can't help with O'Reilly parts numbers.
But I can say that the Tiptronic has an alternator PN that is different than those for manual transmission cars. Go to this link and you'll find the alternator is #23 and is shown as PN 99660301203 for Tiptronic cars 1997-2004:
Battery Power Distributor Starter Generator
This doesn't mean that the O'Reilly/AutoZone units are not universal (will work for both transmissions), it just means that Porsche stocks them separately. I do now know what the difference might be (if any). You can always call ******************************************** and ask them.
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