I used this single groove water pump pulley on my 1967 Mustang with 289 for a few years. There are no part numbers cast into the part. I purchased it specifically as it was the right size to work with my Classic Auto Air System. I'm only selling as I had to switch to a two groove pulley.

The overall diameter of the pulley is 5 13/16". The pulley is 2 1/4" from the front of the mounting surface to the back of the pulley. The center hole in the pulley is 5/8".