“That the following rules shall take effect on the one hundred and eightieth day [July 1, 1975] beginning after the date of the enactment of this Act [Jan. 2, 1975]. These rules apply to actions, cases, and proceedings brought after the rules take effect. These rules also apply to further procedure in actions, cases, and proceedings then pending, except to the extent that application of the rules would not be feasible, or would work injustice, in which event former evidentiary principles apply.”