(e)
In the case of a plan maintained by a labor organization which is exempt from tax under section
501
(c)(5) of title
26 exclusively for the benefit of its employees and their beneficiaries, this part shall be applied by substituting for the term “December 31, 1975” in subsection (b) of this section, the earlier of—
(1)
the date on which the second convention of such labor organization held after September 2, 1974, ends or
but in no event shall a date earlier than the later of December 31, 1975, or the date determined under subsection (c) of this section be substituted.