From my research, Grant Sullen produced a "super-bird" in 1971 or 1972, at the age of 17 by cross-breeding large Rhode Island Reds. There are numerous articles out there describing how mean one particular rooster named Wierdo was. The story about him was featured in Farm Journal in 1971, and was broadcast on CBSon August 15, 1972, under the headlines, "Your A Big Chicken Takes on New Meaning in California." There is no current information available on this breeding line or if Mr. Sullens continued to develop this line further. Below are some of the facts circulating out there about his birds.

The heaviest breed of chicken is the White Sully, developed by Grant Sullens of West Point, CA by crossing and recrossing large Rhode Island Reds with other varieties.http://forums.thepoultrykeeper.co.uk/viewtopic.php?t=858

Found this from a 1971 Sports Journal: But they hang in there, and now comes a story from Farm Journal about a 16-year-old California boy named Grant Sullens who has climaxed a cross-breeding experiment by producing a giant chicken "that's as mean as a hornet in your hip pocket." A prize 23-pound rooster has ripped bits of metal out of his feed bucket, bitten off the tip of a visitor's ringer and shattered an intruding TV camera lens. Young Sullens says, admiringly, "I've kicked this rooster, hit him with a bucket, slugged him when he got me down. But I haven't hurt him one bit." The females are just as tough. Three cats were killed when they innocently walked into the hen coop.

"Big Snow, the largest chicken on record, weighed 23 pounds, 3 ounces, and was of the breed White Sully developed by Grant Sullens of West Point, California, USA, and was owned and bred by Ronald Alldridge of Deuchar, Queensland, Australia, Big Snow died of natural causes on September 6, 1992 -- Source: Guinness Book of World Records and various web sites." http://wiki.answers.com/Q/What_is_the_worlds_largest_chicken