it appears the Federal small block pump used the same pulley 1970-'73 #2951 901

per the Parts Catalog(s): 19-54-86 PULLEY, Pump B/J

1970 (May 1970)
2951 901 - 318 & 340 w/3/8" threaded hole pump shaft (A & B-bodies also)
2951 989 - 318 & 340 w/key slotted pump shaft (B-bodies also)

1970-'71 (January 1972)
2951 901 - 318 & 340, 340 3-2bbl w/3/8" threaded hole pump shaft (A & B-bodies also)
2951 989 - 318 & 340 w/key slotted pump shaft (B-bodies also)

1973 (September 1972)
2951 901 - 318 & 340 w/3/8" threaded hole pump shaft (A & B-bodies also)
2951 989 - 318 & 340 w/key slotted pump shaft (listed as E-body ONLY)

neither of these pulleys are shown in the '69 Parts Catalog
neither are shown as used on a C-body
the 2951 989 is also listed in the '72-'73 Truck Catalog for B/W/D & 225/318/360