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Lots of good questions, Stan.
I don't know the answers to any of them.
But here are some thoughts from someone wondering the same things.
We can guess as much as we want about perceived demand, but tire companies are humorless businesses that exist to make money. Decisions they make that baffle enthusiasts are almost always based on passionless reports from passionless, spreadsheet-wielding accountants. I'm guessing if the numbers were really, truly there, we could buy all the Sportracs we want - at Tire Rack, at Walmart, and probably even have them delivered to our door from the gray truck with the swoopy blue arrows.
I do know you can still buy brand new and period correct Michelin tires for your old 911 - the XZX and, more appropriately, the first ever assymetric radial, the XAS (guess what the 'AS' stands for).
I've never tried the Sportrac (for reasons you allude to), but I've got A LOT of miles on the original XAS, and it was a helluva tire in the day (they were also OEM on the BMW 1600 and 2002). Those beasties kept my butt out of innumerable offroad excursions in my formative years and for that I shall be forever grateful. Better than the Vreds or even as good? Dunno.
But if I'm restoring my old 911 back to period correctitude and I still want to have some fun driving it, I'd go with the Michelins, hands down. Straw-hat-and-blue-blazer-wearing Pebble Beach judges go all weak in the knees at the very sight of them.
Yeah, the XAS is now about eight times as much as the Sportrac, but if you've already taken out a loan for the 911 restoration, what's a few pennies more each month?
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