I've never heard of a 64mm supercharger pulley??? If you get the old bearing pressed out and take it to your local NAPA, they can measure the bearing and match it up for a new one . . . Also I think most bearings have the size stamped right on the bearing.

 

 

Most bearings have a number stamped on them, not necessarily a size. The number can usually be crossed to other manufacturers.

James

 

Pulley bearings are listed in this PDF I did some years back. CLICK
You should be aware that this pulley might fail causing severe damage to area around the pulley, you should at least fit the pulley shield made by one of the members here, Latemodel21 is his handle.
If this pulley is aluminum I would not use it at all. If the rivets are loose do not use it. If the bearing is 55mm diameter you should not use it. The weakness is the wall thickness over the bearing, the material and the dog bone springs.
It should have a 47mm diameter bearing with a 5mm spacer.
All these after market pulleys will fail, the OEM pulley will fail one day, but not likely too soon, although their have been reported failures of them as well.
The earlier produced pulleys are disasters waiting to happen.