Gets hot and stalls out

Just so we're on the same page.
This is about where I'd expect the gage to be after a short drive and the engine still running.
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On a longer drive at interstate speeds, or in stop and go, a reading past center would not be surprising.
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As long as its stable, and not rising under either condition (driving at interstate speeds or stuck in traffic) its within the norm.
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1975 Valiant Operator's Manual. page 10.