based on the information on Llewellyn and Mary mentioned in the previous thread (see :
Marriage Cert) I had another search of the details just to double check the results. The updated familysearch BMD index gives the same results - e.g. no marriages for a Llewellyn Turner in the late 1860s or early 1870s anywhere in Ireland.
There are a couple of grooms with the middle name Llewellyn, but none of these are near to Dundalk.
There also doesn't seem to be any Mary Brodigan marriages in the Dundalk area near to the timeframe you mentioned either. The nearest by date are both during 1877, which I presume is too late to fit your Mary & Llewellyn. The next oldest match is a marriage for a Mary Brodigan near to Carrickmacross (Co. Monaghan) in 1874, although this doesn't seem to cross match with anyone with the surname Turner.
Shane