I don't remember all the particulars; there were fewer incumbents of both parties automatically re-elected in those days. One of the senators who lost re-election in 1970 was Albert Gore Sr. of Tennessee. Conversely, conservative George Murphy of California was defeated by that one-term liberal idiot and best friend of Ted Kennedy, John Tunney.
Evidence of GOP gains following the Goldwater debacle was more evident in 1966, when the GOP gained 47 House seats.