the upholstery should be virtually identical. I could be wrong but the headliner, I think, is slightly different, you'll need to find a headliner from a dart post. same with weatherstripping.
I'm using 68 Valiant interior in my 67. However mine is a 100 series, the interior is almost the same. I believe the dart interior has logos heat stamped into them. Check Legendary thats where I got mine.
windshield and doors will work from a 67/68 dart post only. back glass is unique. 67 windshield trim is a one year only deal. you can and probably should use the later trim with clips cause the 67 plastic trim is pretty hard to find, just need to install clips for the later trim.
ask me how I know.