PART NO.  SPL.PAGE  DESCRIPTION                                                           
51K267     15.A.1    Stud for oil pump, short (2) -[Fin(E)GB46341 except 46045 to 46100]
51K267     15.A.1    Stud for oil pump, short (3) -[Com(E)GB46045 to 46100, then 46342 on]
51K267     sup.1     Stud -oil pump, short (3) -(block assy, engine unit, sup)
51K267     16.A.1    Stud -oil pump (short) (3) -(block assy, engine unit, 1600)
51K267     16.A.21   Stud -oil pump (short) (3) -(block assy, engine unit, 1622)
51K889    15.A.1    Stud for oil pump (long) [Fin(E)GB46044 except 46101 to 46341]
51K890    15.A.1    Stud for oil pump (short)[Fin(E)GB46044 except 46101 to 46341]
51K890    sup.1     Stud -oil pump (2) -(block assy, engine unit, sup)
AEH601     TC.A.1    Stud for oil pump (3) -(cyl.block assy, engine, Twin Cam)

AEH601 - Stud --oil pump to engine block (short) 1500, 1600, 1622, 1800, and Twin Cam)
Length:4-1/8"
Top end thread 5/16-24-UNF x 5/8"
Bottom end thread: 5/16-18-UNC x15/32"

High Strength Stud

Alternate part numbers:
328-725, long (Moss Motors USA)

Note: There was change of design of the oil pump and pickup screen .
Early 1500 engines, up to October 1957, used 2 short and one long studs.
After October 1957, all B-Series engines used 3 short studs.
The short studs have three different factory part numbers, 51K267, 51K890, and AEH601.