Hi Pettsy,
Sorry its took a while for me to reply, I've checked the Dumbartonshire MI's and the following are all the Munn's in them :
ALEXANDRIA OLD PARISH CHURCH corner of Main Street & Church Street, Alexandria.
Against the north wall .
No 3 ; Duncan Thomson 12.10.1867 57 , w Mary Munn 7.3.1891 73 , s John at Brantford Canada 24.5.1886, s ? Stewart at Brantford 4.1.1910, s? Wm at Dumbarton 31.10.1910, da? Isabella at Dumbarton 4.6.1925, da Jessie at Dumbarton 16.9.1931 .
CARDROSS CHURCHYARDNo67 ; (east side ) A (J) J W (cherub, 2 chn);(west side ) And. Munn .7.1764 25.
DUMBARTON CEMETERY;
No 126 ; by bailie John Johnston, w Janet Munn 15.7.1881 62, three chn d. young, s John drowned at Nash Sands off the wreck of the ship Ben-y-Gloe 15.10.1886 24 (p 174 ).
]NEW KILPATRICKNo148 ; ( on top ) 1823, David Munn24.5.1823, by s Walter.
No 149 ; ( on top ) 1821, Mc Murray, w Jean Munn 19.7.1808 75, s Jas18(51) (88) (w Margt Dobbie 1.10.184(

(8)5, s Robt 9.10.(1747) (11) m, s Edw (17).1.18(19), da Margt(1825), da Jean ( all very indistinct for date & age.
No 262 ; (FS) T I M G 1789, Thos Inglis 6.3.1819 69, w margt Gardner 18.4.1838 80, s Jas 5.1.1851 72 ( w Eliz Munn 5.9.1854 7(0 or 6 ).
RHUNo 70 ; a stone for a Law family and son in law Carlin , last entry is Robert Napier Carlin 22.4.1925 66, w Agnes Munn 21.11.1940 78.
Hope thats a help to you
Regards Sylvia