How do you make a Cadillac Margarita?

1 1/2 oz Tequila

3 oz Sweet and Sour

3/4 oz Triple Sec

3/4 oz Lime Juice

Float Grand Marnier

Shake the tequila, triple sec, sour mix, and lime juice with ice. Pour over ice in a salt-rimmed margarita glass. Float Grand Marnier on top. Garnish with a slice of lime if desired.