PART NO.  SPL.PAGE  DESCRIPTION                                                           
53K486    sup.5     Stud -exhaust manifold (2) -(engine unit, sup)
53K486    16.A.5    Stud -exhaust manifold (2) -(engine unit, 1600)
53K490    15.A.6    Stud -inlet and exhaust manifold to cylinder head (4)
53K490    16.A.5    Stud -inlet and exhaust manifold to cylinder head (4) -(engine, 1600)
53K490    16.A.26   Stud -inlet and exhaust manifold to cylinder head (4) -(engine, 1622)

53K490 - Stud - for intake and exhaust manifold to head, long (4) -(cyl.head1500, 1600, 1622, 1800)
Length:1-7/8"
Top end thread: 5/16-24-UNF x 5/8"
Bottom end thread: 5/16-24-UNF x 15/32"

High Strength Stud

Alternate part numbers: 328-910

This one is odd, only because it is fine threaded on both ends.