I was listening to an oldie station the other day and caught California Sun by The Rivieras from 1961. My immediate reaction was that the chorus to Little Honda seems to bear a strong resemblance, especially to the organ riff in the Rivieras piece:
https://www.youtube.com/watch?v=Yy57Xdk9u0o
https://www.youtube.com/watch?v=Yy57Xdk9u0o
Small correction: The Rivieras' version of "CS" (an all-time favourite of mine) went top US five in early 1964. It was recorded and first released as a B-side some time in 1963 (which is why I could have sworn I heard it on French radio in that year).
Might Brian have felt the similarity to the extent of then recording an "alternate" version of "LH"----but eventually deciding against it?