Does a '69 air cleaner look wrong on a '70 Dart Swinger 340

If its Mopar on Mopar and you like how it looks, do it!
Make it your car and if anybody at cruise night says anything, point them in the direction of another car to judge.
Enjoy your car.
Its yours and not anyone else’s!
Most people will be overwhelmed with the awesomeness of the car and not even notice. Don't point it out.
I would definitely do it but I like that look too.
My 2 cents.