Hi Sandra.
Since I originally posted, I've established that both streets still exist although parts have been rebuilt. (there are some links to photos in this thread).
Interestingly, my ggg grandmother was a Sutherland. Originally from Drainie in Moray, born 1794, she moved to Pulteneytown and married my ggg grandfather.
Whether her parents or siblings moved to Caithness, I've not checked yet.
Have you looked for older rellies on IGI and/or SP?
Dave