It was a sportsmanship kind of thing. In the '60s at the Cotton Bowl, Dallas had the opponent's endzone with their team name and logo. In Kansas City, they only had the opponent's helmets at the 35 yd line with the Chiefs helmet on the other 35 with the Chiefs having both enzones painted alike from 1969-71. In the 1971 and 1973 NFL Championship Games in Dallas, they had the 49ers and Vikings' endzone painted as if it were the Super Bowl.