Hello Jack
There are 7 McClure names and 6 of those, all Irish, all came out on the S S Great Britain on voyage 32 which left Liverpool on 9 July 1868 and after a trip of 58 days arrived in Melbourne.
They were - McClure, Miss Mary 30 yrs, no occupation, Samuel 23 yrs Farmer, Sarah 18 yrs, no occupation, Thomas 16 yrs, Gardener, William 50 yrs, no occupation and Rachel 50 yrs, no occupation.
On Voyage 41, S S Great Britain left Liverpool on 27 October, 1973, after 56 days arrived in Melbourne. William J McClure, 21 yrs, no occupation is listed on this voyage. The ship then went on to Brisbane. No nationality is listed for William J McClure.
I hope this is your family. Contact me if I can help anymore.
Merry Xmas! Faith Green