LBJ PRAISES MURIEL HUMPHREY; HHH ASKS ADVICE ON VP NOMINATION; LBJ PRAISES HHH AS VP, EMPHASIZES NEED FOR LOYALTY AND HIS REGRET ABOUT NOT APPOINTING HIS OWN MEN; POSSIBLE NOMINEES: EDMUND MUSKIE, HALE BOGGS, DANIEL INOUYE, TERRY SANFORD, FRED HARRIS