Seeking - and finding - the heart of 'Henry V'; Henry V

New York The fourth and latest Central Park ''Henry V'' is an enterprise to quicken the spirit and stir the imagination. With George W. Martin's admirably spoken chorus leading the way in his plea for ''a Muse of fire,'' director Wilford Leach and his large company transport the Delacorte Theater audience to Shakespeare's medieval world of contending monarchs. Gathering momentum and power as it goes, the current revival marks one of the New York Shakespeare Festival's finest hours. Both in the general approach and in Kevin Kline's sympathetically penetrating view of the young King, the production rides proudly with the text. This warlike Harry is a model of noblesse oblige and royal civility. Endowed with some of the most stirring battle exhortations in Shakespearean drama (notably ''Once more unto the breach...'' and the paean to St. Crispin), Henry V must embody the attributes of a great military leader. Mr. Kline portrays such a leader. Henry's prayer to the ''God of battles'' - with its self-serving recitation of penitential acts - comes nevertheless from the heart of a man facing a test in which all the odds are against him and his men. In such moments, Mr. Kline challenges the resistance of a skeptical age and reaches for the soul of the warrior king. Armed with Shakespeare and his own conviction, this brilliant actor wins the field and carries the day. Mr. Kline projects not only the noble dignity of Shakespeare's Henry but also his humanity (as he moves among his troops on the eve of battle) and his humor (as he proposes to Princess Katherine). His wooing is a model of amour with a light touch. Mary Elizabeth Mastrantonio matches him with a Katherine of exquisite reticence. The darling of the French court is certainly the darling of this production. ''Henry V'' proves principally strongest where it counts most. The King is adequately companioned by the courtiers Mr. Leach has assembled, including Earl Hindman as the Duke of Exeter. In this chronicle play, Shakespeare reveals the darker side of rascals used elsewhere for comic purposes. Falstaff's offstage death is pitifully reported by Pistol's wife, the former Mistress Quickly (Kristine Nielsen). Bardolph and Nym (Adam LeFevre and Larry Pine) are hanged for stealing, while Pistol (Dan Hedaya) is exposed as a cowardly braggart. Robert Macnaughton's clearsighted Boy sees through their chicanery. The production runs for more than three hours, but it moves apace under Mr. Leach's guidance. In a particularly effective touch, he places the French Army deep upstage to sing its jolly songs within earshot of the outnumbered British. When the battles arrive, the stage fills with smoke for the fight scenes staged by B. H. Barry. The revival was designed by Bob Shaw (scenery), Lindsay W. Davis (costumes), and Paul Gallo (lighting). Composer Allen Shawn has added the skirl of bagpipes to the usual flourishes of drums and trumpets. It is a musical plus for this puissant production.