I'm sure I've heard Roger McGuin say that "If I needed someone" was based on his version of the Bells of Rhymney, rather than the other way round. I googled it and found this http://en.wikipedia.org/wiki/If_I_Needed_Someone
which seems to confirm it. There was a lot of cross fertilisation of ideas then as now of course so maybe memories have faded with time -and illegal substances!