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Richard, no cutting necessary!
I'm pretty sure that VM is now installing as standard equipment the new VDO replica-style gauges. They're made by VDO to resemble the old VDO gauges that were in the original 356.
So, you'll have a quality VDO gauge connected to a VDO temp sensor mounted on your engine. It's just a question of learning what the gauge is telling you about your engine's temperature for various positions of the needle.
Cheers!
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