JPI Slimline Oil Temp Gauge

the Ercoupe was certificated under CAM regulations, it is not restricted by PMA rules, if you need a oil pressure gauge, you can install auto style gauges

...I deleted my original question before the reply, since I believe I found the answer....

Original question brief:

The Erco is not on the Approved Model List for the jpi slimline oil temp gauge. Can I still install this gauge?

From the quick search I did on this it appears it does not matter being that the Erco is also not on the AV-30 AML and I see many Ercoupes with this gauge. My next question is will I need a 337 to install the slimline as a primary oil temp gauge?

Ercoupes were originally certified with automotive engine gauges. Neither Univair nor FAA have seen fit to update the requirement (or lack thereof). I'm thinking that means you have to get one from the local Auto store.