I believe you are thinking of the PowerCenter Pro which shipped with a CPU card with a 60 MHz bus speed and 180, 210 or 240 MHz CPU speed (PPC604e).
Some of the other Catalyst based Power Computing models could also be clocked up to similar heights. I don't know if any of them would go all the way to 66 MHz.
On the one hand, all of the candidate machines are Catalyst based (7200 family) rather than being Power Surge machines (x500 family). On the other hand, the 7200 also uses the Bandit PCI bridge and the same arrangement of PCI oscillator and clock buffer, so it should work...