Sunday afternoon update - Time to finally try to fit the Ford tach into the slot.
Here is the tach with a cardboard template, based on the original tach face:
After trimming the excess, the tach fits!!! Still needs some fine tuning, but looking good so far
Back view. Still need to decide how to attach it to the housing, maybe some of those speed nuts or whatever they are called that just push on the posts to keep it in place.
Top view.