Hi Kingseat,
I have a copy of the wee book Sancti mentions, but although there's a few pictures on the Main Street, none show any specific house numbers.
I had a look at a 1960 O.S. Map which shows that the numbers ran east to west which means the low numbers would be at the Garrowhill end.
I think No. 27 would have been around the junctions of Scott Street, South Scott Street and Main Street, on the opposite side if the road from the Police Station.
Anne