Are you sure you got the high
lip model, and not the high
ball one. Look the the top of the case:

Left is highlip, right is highball. Highball lip is level with the wings.
The highball has a wider lip to allow the ball to sit higher, and needs a different mounting plate (55-1104-00).
Also make sure you have the right plate: the highlip plate should have a 3" hole.
Edit: just to make clear, the part numbers you posted should fit. That's why I'm describing the parts.