I don't know why you would care. Older Macs don't really have the speed to properly utilize anything faster than 32-bit, 33 MHz PCI anyway. (The main memory on the PCI PowerMacs is barely faster than 32-bit/33 MHz PCI.)

Besides, all 66 MHz PCI cards are backward compatible with 33 MHz PCI. (And, in fact, 133 MHz, 64-bit PCI-X cards are backward compatible with 33 MHz, 32-bit PCI, as well. So you could, in theory, slap Apple's PCI-X FibreChannel card into a PCI PowerMac, and it would work just fine.)