The engine beds on my '76 I/O were closer to the centerline than that. They extended about 6" inward from the first step towards the centerline. You can see where I cut them out. The outboard edge was about where yours start. On the starboard side there is a wooden pad used for mounting the trim motor - not the same as what you have but looks like it is cut at the same angle and in the same position relative to the keel.
