GMC or Chevrolet?
Chevrolet:
Post links to photos of front/rear of the water pump. That will allow distinguishing new-style (high pressure engines) from old style (low pressure engines):
41 to 52 series (
use this pulley for 53 to 55-1st); and,
55-2nd to 62.
The diameter of the balancer will allow distinguishing newer car from truck and older car. Width of the pulley groove will distinguish years.
The width of the pulley-grooves can distinguish the years that used that width:
5/8" 37-52; and,
3/8" 53-62.
