PowerSteering
You might put a parts wanted ad in the proper section. There's bound to be a good used pump out there somewhere, even if you have to reseal it. I would do that anyway. '64-8 used the same basic pump, although the pulleys and reservoirs may be different depending on the application. '64-6 small blocks should all have the same pump assembly though. Maybe someone doing a manual steering changeover will have their old pump. Good Luck!