Hello Patrick,
Yes, I have often seen Gill and Killey used interchangeably, especially in Maughold records.
Maughold parish register has:
5 Dec 1865
Patrick RODGERS Full age Bachelor Labourer Ramsey [father] Edward Rodgers, Labourer
Jane KILLEY Full age Spinster Ramsey [father] John Killey, Labourer.
Sorry, I don't have post-1849 bapts. or Ramsey register transcripts, but many Ramsey people were included in Maughold records. I can look up burials if you like?
Sue