Crackback Blocks, 1978-1979

[JoeZagorski]

Hey Guys,
Can anyone explain to me how the rules changed between 1978 and 1979 to the legalities of crackback blocks? In 1979, the competition committee extended the zone in which there could be no crackback blocks. Where was the so-called zone in 1978? Where was it in 1979 after the new rule was installed? Thanks for all of your help and information.
Sincerely,
Joe Zagorski

[BD Sullivan]

Prior to the start of the '79 season, the rule change was noted this way:

"The area in which the crackback block is forbidden has been extended from three to five yards on each side of the scrimmage line."