Are these the dates of trial or of actual leaving for Australai?
Did they go to New South Wales or Tasmania?
I have found the trial of my 2 IoM convicts at the LDS, this will give you details of the trials and you can then look in Manx newspapers for reports around that date.
If they went to New South Wales you can go to the State Records Site at www.records.nsw.gov.au/ and look at records on line where there are many convict records including Tickets of Leave, Certificates of Freedom and Deaths in Custody amongst others.
You could check the Tasmanian records also on Google if that is where they went.
The indent of convicts on each transport are available at Kew, the name of the ship and year of arrival plus the name of the Master are shown on the Tickets of Leave and the Certificates of Freedom.
There are also Assignmant registers which should be available at Kew (where the convict was sent to work).
BDM's for Victoria and New South Wales are on line, I have not needed to check other states but they would be available in some form or other.
Last week Frances posted a very useful site at the State Library of Queensland which should help.
You can also look at the National Library of Australia in the digitised newspapers for any record in those papers already there.
Remember that many convicts altered their name, the ship that they came on, their date and place of birth in order to avoid "the stain" of convictism.
Also the original records uaually relied on what the convict told the authorities and they could change these to avoid distress to their family or if they had offended previously to avoid an extra penalty for reoffending.
Peter
Melbourne