You may find this website useful.  I see that my gggrandfather departed Liverpool on 5 Sep 1855 and arrived New Orleans 20 Oct 1855.
(the story is that the family was shipwrecked on a previous attempt, but I have, so far, been unable to confirm that)
http://www.theshipslist.com/Forms/index.shtml
Various buttons on the website may be of use.

Roger Low
London, England
Researching Löw in Bohemia & Moravia