The local poor records may well still exist in storage somewhere, so don't write them off yet unless proof is available that they were destroyed.
Smithston/Ravenscraig was a Canadian Navy base, HMCS Niobe, during WW2, so any records would have been put elsewhere during that period. Apart from the Poorhouse records, per se, they would contain a much more important source for family historians, the Poor Law Applications. These concerned people who mostly were never near a poorhouse. Have a look at the Paisley ones in Paisley Library, or the Lanarkshire ones in the Mitchell Library, Glasgow, to see what I'm talking about.