Sorry, no stones matching, in fact none at all having 'N' as the surname in Muiravonside.
One in Polmont has WN HS and on the reverse side has 1846 Henry Wilson, wife Jean Hogg & Children 1766
I have photos of the Alexander Nimmo & Christian Buchan stone, albeit not very good ones - Muiravonside Churchyard is a nightmare to photograph. I tried during summer and the grass/trees/overgrowth made it difficult then during the winter, the light just isn't good enough to capture the details. Your more than welcome to copies of the photographs of this stone, send me your personal e-mail via PM and I'll send them through.
Anne