Ah, I see my mistake. The steering box support bracket was present on the earlier cars, it just changed when the 3A was introduced. The spacer was only on the later cars, though. The early bumper supports were flat, so the steering box support fit flat against the bumper support. But the later ones were U-shaped, so the spacer was needed to fill in the gap. And the support bracket had to kick out farther to pass over the U-shaped bumper support/frame extension.