Many changes to help the offense now. The Mel Blount rule, the amount of holding the offensive lineman are allowed to do now, no hands to the face, no head slap, no hitting the qb comapred to then, defenseless receivers, no crack back blocks by the offense. Before you guys get all wrapped up in the present linemen remember the steelers had the two strongest men in the nfl on their line, John Kolb and Mike Webster. The 70s Steelers were the best by a big margin. Rules favored the running game in that era. A young Bradshaw would have tremendous stats in today's game with his receivers not getting mugged the whole game.
Some players could go from this era and play the 70s game but not a lot of them. Pouncey might be the fifth best center the team has had when you consider those that played in front of him, Hartings, Mullins, Webster and Dawson. Dawson was truly great and was likely the best ever who had both speed and power. Possibly being fifth on that list is not a bad thing as all of those guys were fantastic players.