You can change the display name during the import to your standard last name, first Name.
To modify the display Name Syntax you use the option “Build Properties” You can create values by concatenating other property values. Choose the property and select the option BUILD PROPERTIES.
In the textbox BUILD PROPERTIES, add a string, how the property value should be built.
Via the ADD PROPERTY button, you can choose which properties are used. For Example, you want to generate the property, DISPLAYNAME from the last name, and first name comma separated. Choose the property SN and the property GIVENNAME and insert a comma and space between them in the textbox BUILD PROPERTIES.
Please make sure that this rule is only valid for source objects, which are users and contacts, because groups have normally no givenname and surname (sn).
For more information please have a look into the GALsync manual http://www.netsec.de/fileadmin/download/GALsync/GALsync_Manual_EN.pdf