Old gauge? As in stock?
I'm thinking about just going with this: https://www.autometer.com/universal-triple-2-1-16-dash-pod.html
I need to take some measurements, but it looks promising.
Here's mine, currently (wish that Roush gauge had a black bezel) :
My current set up is six aftermarket C2s on their own dimmer. I have boost/vac, fuel pressure, air/fuel, oil temp, oil pressure, and water temperature.
Once I get the pod figured out, I am planning to add: intercooler water temp, volts, and tranny temp. I already had the custom gauges made so they all match the OEM gauges.
I also have a Boss 302 Laguna Seca pod from Ford Racing in hand. Just debating mounting this myself or going with the other setup you found. Kind of afraid to hack up my own center pod.