What sender are you non P-motor guys using to use the original oil temp gauge as a water temp gauge? Mine is a Chevy V8 in a 1976 if there is a difference.
I have tried several VDO senders. The closest I can get is their 323-057
It is their 0-150C (0-300F) sender. The problem is that it centers the needle at 75C (165F) so at normal operating temps, the needle is about midway to the right of center.
Their 0-120C sender exaggerates this even more. Their 0-200C sender centers the needle, but won't give me much warning if I start to over heat.