108 wb versus 111 wb leaf springs

Ok now i'm well confused, I thought Dusters were 108 and Darts(except the Sport) were 111???? The year I'm talking about for my car is 1970. The reason I had asked in the first place is that I knew or thought I knew that Darts were 111 because I wanted to buy some prefabbed frame connectors from another FABO member and knew that the ones for my Dart had to be 3 inches longer than 108 wb cars. I had also heard once that you could force the 108 springs onto a 111 wb car but that it was a major frig and that the shackle hangers were in an odd position when you were finished.