He is 73; she is 32. He is 6'4" and she is a foot shorter. He is a world-famous pediatrician, political radical and best-selling author. She is a former schoolteacher. He wanted to get married. She didn't, asking, "Why bring the government into it?"

The attraction of opposites resulted in Dr. Benjamin (Baby and Child Care) Spock and Mary Morgan Councille taking out a marriage license in Little Rock, Ark. They set the date for Sunday, Oct. 24. A feisty women's libber, the bride said she would not adopt Spock's name and would be known as Mary Morgan. "I have strong negative feelings about the trips society puts on a marriage," she says.

Spock, divorced earlier this year after a 48-year marriage to Jane Cheney, met Mary Morgan in April 1975 at the University of Arkansas. "I thought he was too old," she recalls, but decided after his talk, "This is someone I can learn from."

That same month, three years after the end of her 10-year marriage to Dr. Clifford Councille, she moved to Palo Alto, Calif., where she launched a career as an organizer of educational conferences. Spock accepted an invitation to a session on the abuses of power. "That was the week," he says, "we fell in love." (He did not, however, remember Mary from Arkansas.)

Spock, a resident of the Virgin Islands, and Mary Morgan are building a house at Esculapia Hollow, Ark. to be near her daughter, Ginger, 11, who lives with Dr. Councille. "We can't think about having kids," says Mary Morgan. "We're thinking about sailing, honeymooning and campaigning."

Spock is the candidate for Vice-President of the People's party, and the stump is a familiar place to his wife also.

She has crusaded for ERA and wants to move on to the problems of blacks and the elderly. Spock admits his party, which is on the ballot in only six states, is "in disarray."

Arkansas is one of the states where voting for Spock will not be possibleā€”at least as of now. That, notes Mary Morgan, is another issue she hopes to do something about.