I would think this has been done...

Figured that in order to get my MPS dialed in correctly I need to make sure I have my engine temp operating within normal range...

Do you mean a head temp gauge, or an oil temp gauge? If oil temp, are you referring to replacing the e-brake light in the combo gauge with an oil temp gauge?

Note that these two things are not measuring the same thing, as oil temp does not equal "engine" temp exactly.

For tuning an MPS, a wideband O2 sensor would be much more useful than a temp gauge.

I'm speaking of oil temp gauge - like the ones that go in the center console (although I have no intention of getting a center console).

A wideband 02 sensor is on my list of things to get - something like an LM1.

-pt

If you can't find a 914 combo gauge with a temp gauge out there (they exist), then
you can buy a 911 or 912 oil temp gauge used (or a combo gauge for a 911 or 912), and the oil temp gauge will fit into the upper half of the 914 combo gauge. They're all modular. A matching sender can be ordered from many places. There's a part number on the gauge face itself, and there's a cross reference table around here somewhere (search). You'll also need to find a "taco plate" from a later engine, which has the mounting point for the sender. This is on forward end of the sump, driver's side.

The wiring is very likely on the car already. Look for a green/black wire behind the combo gauge in the dash (the gauge just pulls out, held in my a rubber ring) that's not connected to anything. If you can't find one, look for a brown/white wire instead, and look for a matching unconnected brown/white wire in the engine bay. The early cars often had this wire, which was for the Sportomatic that was very rarely fitted.