This film is from circa 1965. Even in 1990, the Vulcan/Chaparral/FAAR team formed the backbone of the armored/mechanized infantry division’s Air Defense Artillery battalion, though by that time, there were also several FIM-92 Stinger missile teams available.
Some of the platoon and company life fire gunnery ranges at Graf in Germany were especially fun when, as a dismount grunt, I could stand right next to an M163 Vulcan, and watch it dispatch bursts at targets.
By 1990, both systems were clearly obsolete, and would be hard pressed to successfully engage most any Soviet aircraft, and even struggle with helicopters such as the formidable Mi-24. The Vulcan had been slated to be replaced by the M247 SGT York 40mm gun* but the failure of that program meant the Vulcan and the Chapparal eventually were both replaced by the Stinger missile, and a lot of hope that Stinger would be enough.
*Which, the Vulcan itself replaced the earlier M42 40mm gun carriage, popularly known as the “Duster.”