Those are also the same temp sensors I used in my FL350. I just swapped the radiator one from a 170 to a 150, no spill. I love how easy they are to change.
As far as the bung, I have no idea. I had to use a metric to npt adapter for my radiator though. Here's a link to what I used:
https://www.amazon.com/gp/product/B07DN ... UTF8&psc=1The Yamaha Grizzly radiator I used on my FL350 was pre-tapped at M18X1.5, that's why I went with this adapter. Maybe you'll get lucky, but I'd bet dollars to donuts the existing threads in yours are metric.
EDIT: Here's a closeup of the whole she-bang in action, you can see it's pretty deep into the water jacket this way:
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temp_sensor.jpg [ 58.01 KiB | Viewed 1027 times ]
Good luck!