P205/75 R14 or P215/70 R14
I have 215 70 14 on stock 5.5 wide factory steel wheels on my 67 Dart. And KH front disk. ( KH disk widen the track by 1/2 " each side IIRC)
They fit well but look a bit ballooned.
Not sure if there are any significant differences 67 Dart to 74 duster in the fender area.