I mentioned some time ago that I was in the process of trying to work out if I should re-furb my existing Smiths speedo and tach, which are pretty beat up and faded, or buy new EMGOs.
To have the Smiths clocks re-furbed was $225 each.
To buy new EMGOs was $65 each.
The web sites selling the EMGOs made it clear that the EMGOs were 1/4" deeper than the Smiths and were not just a drop in replacement.
Fitting the EMGO clocks to the OIF cups only needed the two rubber 'nubs' in the cups to be removed with a craft knife.
The clock then just pushed into the rubber cup and the top edge of the cup sealed around the bezel.
The speedo needed a hole cut into the cup for the tripometer reset, but the cup is profiled at the right point.
Nothing to fear, apart from stabbing yourself with the craft knife. Don't do that.
I am going to make up some 3/16" alloy spacers so the the clocks can be 'bolted' to the cups without crushing the rubber,