I think we can all agree that Superformance didn't pump out in excess of 500+ cars from Jan 1, 1999 to early 2000. Especially since they haven't built #3,000 yet (real close though if not already being built).
Something is screwy with the numbering here.
"My 2003 SPF is #1560 (Feb. '03 delivery)". Assume for a moment that #747 was, in fact a Jan '00 build. That's a span of 813 cars across three years, or 271/yr or ~23/month. That sounds more realistic to me. So the mystery car in question is still in my mind just that, a mystery.