The number 2 song in Australia on 7 July 1978 was "Mull of Kintyre" by Wings.

Context

That 1978 Australian singles list shows "Mull of Kintyre" as the second-ranked song for the year overall, and it was a major hit in Australia that year.

Note

I can also help with the full top 10 for that date if you want the surrounding songs.