Diane,
the name Spellman is most unusual here so I searched www.rootsireland.ie for William.
I found a baptismal record for a William Spellman, father Patrick Spellman bap. 1832 in Co. Limerick. I then went to the Limerick genealogy site and searched to find out in which parish he was baptised. He was bap. in Doon RC. this is on the border of Limerick and Tipperary.
I think it would be worth viewing this record as the surname is so unusual. I don't know how sure you are of your dates, but I would advise you to keep a very open mind. Dates found on census records and tombstones have in the past turned out to be inaccurate in many cases.
Most people who emigrated were illiterate and undocumented. They didn't know how to spell their names and hadn't a clue as to what age they were. At the port of arrival their names were recorded phonetically, their ages were only guessed, and this is the information that followed them for the rest of their lives.
The proof of this occured in 1909 when the old age pension was introduced into ireland. People had to prove their ages and were forced to go through baptismal records to establish when they were born. That is why there is such HUGE discrepancies between ages in the 1901 census and the 1911 census of Ireland. Dates were found to be out by many many years in some cases.
Hope this helps you in some way,
anne Dennehy