I'm using a gauge I got from George that fits correctly with a 60mm core, but it doesn't have a scale. I was thinking I'd get a meat thermometer with a long cord and dropping it down the oil tank. If I did it before and after a drive, I could kind of calibrate the gauge My concern is that the tank temperature would be significantly different than the case.

I bought a dipstick thermometer from one of the members here, sorry don’t remember who but someone might chime in.

You can get a non contact infrared thermometer pretty cheap these days, it comes in handy for a lot of stuff

But where do I take the reading. Is the body of the case good enough?

I would think the sump plate would be the best place, but not the easiest to get to.

Used to be Mainely Custom. They were purchased by Precision Matters.

https://precisionmatters.biz/type-4-dipstick-thermometer.php

Shows in stock.

Get it up to temp and pull the dipstick

Oil tank ?
Six cylinder temp is measured with a sender threaded into the block near the fan.
Gauges with a numbers are available for Porsche instruments, VDO aftermarket
and others.
Or....do you have a dry sump 4cyl. ?

Point the infrared at the bottom of the case, it doesn't have to be at the plate. A thermometer would need a long lead to reach the oil in a tank, plus a small head you risk dropping it into the tank.