Single player make all heads the same digit (in order to have only the one head to replace and be on all the guards)

Dam
All Guards
811DFDD2 00XX
5000231C 0000
811DF9FE 00XX

Facility
All Guards
5000311C 0000
811CFE16 00XX
50000B1C 0000
811D0372 00XX
5000041C 0000
811D0566 00XX

Runway
All Guards
5000101C 0000
811D8416 00XX

Surface 1
All Guards
5000041C 0000
811E1986 00XX
5000051C 0000
811E1AA2 00XX

Bunker 1
All Guards
5000151C 0000
811D2726 00XX
5000021C 0000
811D29AA 00XX
One Guard
811D2726 00XX

Silo
All Guards
50000F1C 0000
811CD2B2 00XX
5000031C 0000
811CCC06 00XX
50000A1C 0000
811CD196 00XX
One Guard
811CCC06 00XX

Frigate
All Guards
5000291C 0000
811EC9E6 00XX
5000061C 0000
811ECE62 00XX
One Guard
811EC9E6 00XX


Surface 2
All Guards
5000071C 0000
811EEBBA 00XX
One Guard
811EEBBA 00XX 

Bunker 2
All Guards
5000061C 0000
811E0176 00XX
5000071C 0000
811E0402 00XX
5000051C 0000
811E02CA 00XX
5000061C 0000
811E0662 00XX
50000A1C 0000
811E07B6 00XX
5000021C 0000
811E0572 00XX
One Guard
811E0176 00XX

Statue
All Guards
5000041C 0000
811DFEDA 00XX
One Guard
811DFEDA 00XX

Archives
All Guards
811D5056 00XX
5000021C 0000
811D4ECA 00XX
5000041C 0000
811D5072 00XX
5000061C 0000
811D4F02 00XX
5000051C 0000
811D4914 00XX
One Guard
811D4914 00XX

Streets
All Guards
50001F1C 0000
811CBDFA 00XX
5000071C 0000
811CC17A 00XX


Depot
All Guards
50000E1C 0000
811EEE66 00XX

Train
All Guards
50001F1C 0000
811C5616 00XX
5000031C 0000
811C5A5E 00XX
5000021C 0000
811C597A 00XX

Jungle
All Guards
50000F1C 0000
811B0DD2 00??
5000121C 0000
811B0B76 00?? 

Control
All Guards
50001A1C 0000
811D9D46 00XX
5000051C 0000
811DA01E 00XX
5000081C 0000
811DA0DA 00XX

Caverns
All Guards
811CDB06 00XX
811CE64E 00XX
811CE676 00XX
5000041C 0000
811CDAE6 00XX
5000051C 0000
811CDC72 00XX
5000051C 0000
811CDD7E 00XX
5000071C 0000
811CDE8A 00XX
5000051C 0000
811CDFCE 00XX
5000051C 0000
811CE0DA 00XX
5000131C 0000
811CE1E6 00XX
5000091C 0000
811CE406 00XX
50000B1C 0000
811CE50E 00XX
5000051C 0000
811CE742 00XX

Cradle
All Guards
5000051C 0000
811D8476 00XX

Aztec
All Guards
5000271C 0000
811DFC3A 00XX

Egypt
All Guards
50000E1C 0000
811D01B2 00XX

Credit to SeaSalt, the long lost PAL hacker.  Kudos.