I bought a complete steering wheel from a 68 Valiant for my 67 Valiant a couple of years ago. The centers on both where twist on. I could put the trim ring and horn button on both wheels.
I could also mix the the horn buttons with the trim rings with no problem. IE, the 67 horn ring with the 68 center cap, the 68 horn ring with 67 center cap.
My guess is that the Darts wheels where built similar.
