60-79: Defensive linemen and offensive linemen other than centers
80-89: Wide receivers and tight ends
Numbers 0, 00, and 90-99 are no longer allowed to be issued, even though these numbers were rarely issued anyways. Numbers 90-99 would be allowed again in 1984 for defensive linemen and linebackers in addition to the above mentioned numbers.
Defensive players cannot jump or stand on a teammate while trying to block a kick.
The clock is to start at the snap following a change of possession. Previoulsy, the clock would start on a change of possession when the ball was spotted ready for play by the referee.
If there is a foul by the offensive team, and it is followed by a change of possession, the period can be extended by one play by the other team.
If the receiving team commits a foul after the ball is kicked, possession will be presumed to have changed; the receiving team keeps the ball.
Starting in 1970, and until 2002, there were three divisions (Eastern, Central and Western) in each conference. The winners of each division, and a fourth "wild card" team based on the best non-division winner, qualified for the playoffs. The tiebreaker rules were changed to start with head-to-head competition, followed by division records, common opponents records, and conference play.