SPARKMAN TELLS LBJ, LADY BIRD JOHNSON THAT LBJ'S SPEECH WAS BEST HE HAS MADE EXCEPT FOR LAST 15 SECONDS, SAYS HE HOPES LBJ WILL RECONSIDER DECISION NOT TO RUN; LBJ SAYS DECISION IS IRREVERSIBLE; SPARKMAN'S DAUGHTER'S CAMPAIGN WORK AS SERVICEMAN'S WIFE