The car didn't come with an oil pressure gauge. It just had an idiot light. An oil pressure gauge wasn't even an option until they started putting the Rallye dash in them. I'm not sure what year that was. Maybe 1970? I don't want to have extra gauges mounted in pods under the dash so I had to think of how to mount an oil pressure gauge and have it not look out of place. A popular mod for these cars is replacing the factory AMP gauge with a 2" VOLT gauge. I decided that an oil pressure gauge was more important than a VOLT gauge so I set out to do the conversion.
I purchased a 2" SunPro electric oil pressure gauge and gutted it. The + and- terminals of the gauge were the same distance apart as the factory AMP gauge so it would fit in the same spot. The third sending unit terminal was a problem though. My original plan was to cut the sending unit terminal very short so it would clear the back of the gauge cluster housing. The printed circuit is directly behind the AMP gauge so this is why I originally planned on doing it this way. The + and - terminals of the AMP gauge stick through the printed circuit. After looking more closely, the sending unit terminal would clear all the traces on the printed circuit if I drilled a hole in it. So, I ended up drilling a hole through the back of the cluster housing and through the printed circuit body.
Here is the 2" gauge mounted in place of the original AMP gauge.
Next, I removed the gauge face from the new gauge. It's just held on with two small screws. I used the face as a template to modify the original AMP gauge face so the oil pressure mechanism would clear. Here is the gauge without the face installed. It just barely clears the blue dash light lense.
I had to drill two new mounting holes in the AMP gauge face so I could attach it to the oil pressure gauge. Here is the original AMP gauge face mounted. The face is white because I was experimenting with repainted the gauge faces. I will be cutting off the original AMP gauge needle and gluing it to the new oil pressure gauge needle so it will look just like the water temp and fuel level gauges on the other side of the dash. Just to the right of the AMP gauge is the idiot light. I'm going to keep that functional as well. I'll just "T" off of the port on the back of the engine and run both sending units.