There may be many famous 1970s couples but the only one i can think of is "Sony and Cher". Check the internet for pictures of them to see if they would fit what you want to represent. Or, you could pick a political couple.
Valkyries.
Amelia Earheart
Hall and Oates were made the most famous for their music in the 70s and 80s. They are a duo team that pairs up to sing and record music songs together.
You can always do the Classic Romeo and Juilette. But you should pick something that goes with your personalities and interests. You could go as the Flinstones or the Jetsons if you both appreciate the old cartoons or any other couple from a movie or cartoon you both like. Or if you both are into Sci fiction you could go as Spock and Uhara. If you are both interested in politics- you could dress up as the Kennedys or another political couple. Going as a music couple (Sonny and Cher) or a movie star couple (Brad Pitt and Angelina Jolie) would be a fun way to express your intrests as well. Don't forget you can always choose something less traditional- Salt and pepper are technically a couple too! As is ketchup and mustard. Hope this helps!
Lady GaGa
You might dress up stylishly. You could make a splash and dress up daringly. Or you may dare to dress up barely. You could dress up horribly. You may like to dress up cutely. Or, perhaps dress up acutely.
dress up lizzy.com dress up lizzy.com
dress up i think it is both because it depends on the the way the person that pronounced it said it
"Dress up" has 2 syllables. Dress (1) up (1).
Maria Carey? Marcia Cross? Miley Cyrus
Supercharge
a big puff dress and put your hair up and curl it