Ok, pictures might help...
This is COB6008, speedo and tacho on same horizontal plane:
This is COX6111, with tacho significantly lower than the speedo:
This dash is not a dropped-centre dash like COB6008, so the clock is non-standard, but I don't think that has a bearing on my question.
I notice that ERA speedo/tacho locations follow this layout.
Cheers!
Glen