Craig
Rotated fast? I think you must be dreaming about these old trucks being able to go fast:).
But I have no idea if they will stay on well, I bought repop hubcaps and they came with painted emblems. But it is one way to get nice straight edges. And not terribly expensive to find out.
I was thinking, if you still want painted emblems, you could paint the whole center section of the hubcaps black, apply the decal over the black paint, then spray the entire thing gray. Then remove the gray-painted decal carefully, and the lettering should be black with nice straight edges. I have never tried this, would it work you think?