The SA births index does have TAYLOR as the maiden name on two records.
This is what is in BISA.
EYERS Isaac par: Isaac b: 1835 DOR ENG
arr: 1856 LORD RAGLAN occ: Labourer, Farmer
res: Dairy Flat rel: Wes
m: 23.10.1860 Dairy Flat SA Marion nee MACK
CLOUD par: Angas b: 1830
Maybe the parents????
McLEOD Angus b: c1795 Stroud, Harris SCT
arr: 1853 HERCULES occ: Shepherd
m: by 1853 Ann b: c1796 Stroud, Harris SCT
TheShipsList, Immigrants to South Australia, (UK, assisted passage) 1847-1886, have several Marion McLEODs arriving in 1853 on the Neptune and others in the family arrived on the Hercules in 1853.