NFL Connections #75, Answers
The full solution: all four groups and the 16 names, sorted from the easiest group to the trickiest.
1970s star QBs
Terry Bradshaw, Roger Staubach, Ken Stabler, Fran Tarkenton
1970s star running backs
Franco Harris, Earl Campbell, Tony Dorsett, Walter Payton
1970s star receivers
Lynn Swann, Drew Pearson, Harold Carmichael, Cliff Branch
1970s star defenders
Joe Greene, Alan Page, Jack Ham, Jack Youngblood