Thanks for the replies.  That is helpful.  The AM/PM doesn't use a space after the time, so I revised as below.  Not sure why the '0' + was added since it was always removed by the outer function.

IF (@dateformat = 7)

 begin

 set @converteddt =

  STUFF(right( convert(varchar,@datevar,100 ) ,7), 6, 0, ' ')

  set @formatexists = 1

  end