THE FIRST IMPRESSION on the embarkation platform of the Magic Skyway promises fantasy and high adventure, for although the seventy-foot platform is obviously moving, guests appear to be standing still in relation to the Ford and Lincoln-Mercury convertibles gliding in to pick them up for their exciting journey. The explanation is quite simple and not a little bit ingenious: boarding passengers and cars are moving at exactly the same rate of speed, thus assuring maximum ease getting in and out and a substantial reduction in waiting time.   This is typical of the comfort and convenience built into the entire Magic Skyway ride. No effort is required of the passengers, even the person in the driver's seat, for the engineless cars are powered and guided by an electronically controlled mechanical system operated from a central control panel. Even the narration describing highlights of the ride is piped into the radio of each car, and should guests be visitors from French, German or Spanish speaking lands, a touch of a button brings the narration to them in their native language.   Thus with nothing to do but sit back and relax, passengers may concentrate on enjoying the new adventure of the Magic Skyway that awaits them. WHEN WALT DISNEY and his staff were planning and creating the entertainment for the Ford Pavilion, he remarked that it was his desire "to provide guests an entirely original experience, something no one has ever seen or done before."   "It could never happen in real life," he admitted, "but we can achieve the illusion by creating an adventure so realistic that visitors will feel they have lived through a wonderful, once-in-a-lifetime experience."       Traveling through the first "time tunnel" on the Magic Skyway is an appropriate example of his expression. The illusion is that passengers are being projected though space and time at tremendous speeds to some unknown and unseen destination.   Those who would prefer to preserve their illusion may choose to stop reading at this point. Those who don't may be interested to know that the sensation of spaceship speed was achieved by flashing stroboscopic lights moving rapidly from the opposing direction and triggered by timed circuits and heightened by stereophonic sound effects. Illusion, yes, but also the essence of exciting entertainment.   GUESTS MAY LONG remember the moment they burst forth from the "time tunnel" onto scenes of primeval splendor, enormous, animated beasts, volcanic eruptions, and then to the emergence of the caveman and other animated and realistic scenes of his conquests, struggles, discoveries and inventions.       This is the adventure that Walt Disney referred to as "so realistic, visitors will feel they have lived through a wonderful, once-in-a-lifetime experience."   Bringing the prehistoric world to "life" was achieved by Mr. Disney and his WED Enterprises staff by developing a remarkable technique called "Audio-Animatronics" -- animation powered by sound and controlled by electronics. Movements and sounds of the cavemen and animals are programmed onto magnetic tape. As the tape sends signals into a caveman's body, for example, each sound impulse triggers an air valve, shooting highly compressed air through plastic tubes connected to an intricate system of springs and levers that act like muscles, thereby controlling actual movements.   One final touch of realism. The chemically processed "skin" of the cavemen has the touch of human skin, "perspires" as a human and even "bruises!"   Source: VIP Souvenir Book (presented courtesy of Gary Holmes) Illustrations: &COP The Walt Disney Company   LEAVING THE STONE AGE, guests dip into a second "time tunnel," and now are vaulted far into the future to emerge on perhaps the most impressive illusion of all -- Space City. After the initial impact of a kaleidoscope of colored and moving lights, soaring architecture and seemingly suspended highways, passengers suddenly realize as they glide and wind their silent way high above and through the futuristic city, that they have been joined by other cars and passengers on the highway in the sky. Forty cars and passengers are visible at different heights, distances and angles, creating the shared feeling of exhilaration and awe at having indeed taken an exciting automobile ride into the future.