I laugh at all the advertisements that say “optional” equipment on 1968 Shelbys.
Here are your choices: bodystyle, engine (model), exterior color, interior color (limited) transmission, ac or not ac
Everything else was standardized or mandatory; power steering, power brakes, tilt, rear axle ratio, ram air on KRs, fold down seat on fastbacks, power tops on convertible with glass, full sized spare ;-), hubcaps, AM radio ( with very few exceptions ) , intakes and carbs, smog...