Used GM pulley.  This is GM# 3162825.  This is a 4-bolt, single groove water pump pulley, approx 6 1/8" outside diameter, 5/8" center pilot, and approx. 2 1/8" deep (when measured on a table).  Universal GM applications, mostly in the 60's for non-A/C and non-power steering applications.

The item in the photo is the exact item being sold.