In case the OP would like to use google maps/streetview to see where they lived.
Australian Electoral Roll
Queensland
1925 Herbert/Mackay
GRAY Marguerita Lister House Home duties
1930 Herbert/Mackay
GRAY Marguerita Mt Bassett Road HD
GRAY William Francis Duncan Mt Bassett Road Seaman
1932, 1934, 1936, 1937 Herbert/Mackay
GRAY Marguerita 9 Peel Street HD
GRAY William Francis Duncan 9 Peel Street Seaman
1943 Herbert/Mackay
GRAY Marguerita 65 Juliet Street HD
GRAY William Francis Duncan 65 Juliet Street Master Mariner
1949
GRAY Marguerita 65 Juliet Street HD
Did Wm have a brother Thomas Alexander
GRAY?
http://nla.gov.au/nla.news-article169972723Daily Mercury, Mackay 14 Feb 1930
http://nla.gov.au/nla.news-article170270054Daily Mercury 25 Mar 1937
Daily Kennel News.
http://nla.gov.au/nla.news-article172571927Daily Mercury, Mackay 2 Jul 1937
The challenge-winning setter dog shown by Capt. W. Gray was an out standing specimen with an extra good headpiece, nice shaped skull and occiput bone, a beautiful type, and nice even color, and could have won at the Sydney Royal Show this year. It should go a long way in its career.
http://nla.gov.au/nla.news-article169409721Daily Mercury, Mackay 20 Oct 1938
IRISH Setter Puppies by Ch. Shamus of the Gladdagh, son of the late Gr. Ch. Brian of Halcana (imp.). Dams: Ch. Maureen of Mourne and Maureen of the Gladdagh. Inspection invited; prices moderate. Capt. W. Gray, 65 Juliet Street, Mackay.
WW2 Service Summaries - Army
http://www.ww2roll.gov.au/Veteran.aspx?serviceId=A&veteranId=78872http://www.ww2roll.gov.au/Veteran.aspx?serviceId=A&veteranId=112670Cando