[PGSigns]

There is something else going on. The high performance GM big blocks ran deep grove pulleys to help keep the belts on. Nothing wrong with a deep groove pulley. I would look at the crank and water pump pulleys for wear. If one has a bad wear pattern in it it will eat the belts. Also you can over tighten the belt and speed up the failure if a grove is worn out. The lean in the top of the belt on the alternator looks like it is being caused by the water pump pulley. I has a lean in it also.
Jimmy