[davepl]

Originally Posted by Livrat

It's because the factory truck speedo had the numbering screened onto the plastic lens and the van speedo has the numbers screened on the face of the gauge itself.

Moreover the mechanism that drives the needle is intended for one of the faces and not the other. There's no "standard" for degrees per mph or anything, so its a crapshoot as to what one mechanism's needle will do with a different mechanism's face plate.