PART NO.  SPL.PAGE  DESCRIPTION                                                             
ARH898    15.C.1    Stud -grille retaining -(case+grille assy, cooling system, 1500)
ARH898    16.C.1    Stud -grille retaining (upper)(2) -(grille assy, cooling system, 1600)
ARH898    TC.C.2    Stud -grille retaining (upper)(2) -(grille assy, cooling system, Twin
    Cam)
ARH899    15.C.1    Stud -grille lower fixing -(case+grille assy, cooling system, 1500)
ARH899    15.R.18G  Bolt -grille to shell (2) -(grille assembly, 1500)
ARH899    16.C.1    Stud -grille fixing (lower)(2) -(grille assy, cooling system, 1600)
ARH899    16.R.18G  Bolt -grille to shell (2) -(grille assy, 1600 and 1600-MK-II)
ARH899    TC.C.2    Stud -grille retaining (lower)(2) -(grille assy, cooling system, Twin
    Cam)

Notice Items 28 and 29.
Item 28 is ARH898 - #10-32-UNF square head stud, zinc plated.
Item 29 is ARH899 - #10-32-UNF round head square neck carriage bolt, chrome plated (alternately called Stud or Bolt).

For more information about the MGA grille assembly see BD-102E.