Well the spoiler curves alot. which looks good on that car because the back end curves alot. personaly i think it would look pretty ugly. but each to his own.
now it might look okay on a barracuda with the nice curved back portion.
I think it would be best to get one and mock it up. Then it will be much easier to say yay or nay. But the Dart is a very boxy style of car. I'd say the curved wing wont work,but what the heck,try one out!
Personally I think it would look out of place like the big air foils that the tuner boys put on the zoomie cars. Would be better to find a period correct one in my opinion.
I have to say I'm just not feeling it for the 67-69 at this point. The curve of the spoiler throws me off a bit but I wonder more about the width and how it angles back from the front base to the top back edge and how it would look from a profile. Hard to say though without seeing one mocked up...
I'd say it would look better on the barracuda...
I'm not sure about the dart...
I think the pics that were 'choped may not be scale.
Because I've worked on a new charger at the body shop.. And those spoilers are pretty big...