Interesting - I hadn't given it a thought. - but thanks for the heads-up.
So I googled around, and there are numerous posts on different forums - including a Vette forum - about the Quanta belts stretching, twisting, and/or "flying off".
Whether that's still an issue years later, I can't tell, as there were no posts more recent than 10 years ago.
I'll have to see if anything else pops up before I install the things, and the existing belts appear fine and operate quietly anyway.
My thought at the time was to put the most correct ones I could find on the car; but I won't run junk if that's the case.