agray1949, I agree that the age looks like 64. This implies he was born 1785/86. He is recorded as 55 in the 1841 census which is consistent. His death is recorded in the Preshome Catholic registers as 31 Mar 1850 (at Baads, Cullen) - annoyingly his entry is about the only one where no age is given!
His wife was born 1782/83 per 1851 census and MI, so a few years older.
Grandchildren were born/baptised as Catholics, and indeed Spences seemed to be mainly Catholic, so I wonder why the parents would be buried in the Old Kirkyard?
My interest was in their daughter Helen Spence who married John Geddes (no relation of mine) - the marriage was proclaimed in both the Parish Church and Preshome Chapel; their daughter Margaret Geddes married James Taylor Clark (who is a relation of mine) - they married in the Free Church.