It's important to note that a standard highball glass is tall and skinny and holds about 9 ounces. Many of the tall glasses you find are 12-16 ounces, and some almost 20!
To make a 2-quart pitcher, adjust the ingredients to: 6-ounces for each alcohol, 12-ounces of sweet and sour mix, and 16-ounces of cola (more to top off if needed).
Be careful when enjoying a Long Island Iced Tea because the alcohol content is quite a bit higher than most highball drinks. So be sure to enjoy them responsibly.