Temperature senders?

Hi y'all.
I have concluded that the temperature sender on my new engine is not compatable with the gauge in my car. It reports hot when a probe into the oil says it aint!
So, I have the original sender that matches my gauge from my original engine but its stripped (and is the sump type whil teh new one sits in the case). It has numbers T4806 on it.
How do I work out what resistance range it is?
It is as simple as putting a ohm meter on it while heating it up and ensuring a new one maps out the same?
Can gauges be calibrated for the particular sender?
Other than Howard instruments who in melbourne knows about this sort of stuff?

http://www.autoinstrumentrepairs.com.au/
they are in glenvale cres, Mulgrave
these guys are really good.
you need to match the ohms to the guage, and they can work out what the guage has, and order you a sender to suit.

again ask and you shell be told love you guys and gals so much knolage here

to work out the resistance range of the new sender you are correct. put a multimeter on it as you heat it up to get the range it operates over (matching it to the gauge of course).
eg.. if the gauge is scaled from 50-150deg C then that is what you need to test the sender at and see if it matches the gauge requirements. if not the gauge can be recalibrated to suit the sender - depending upon the type of internals in the gauge. some of the cheaper stuff will not be able to be recalibrated as the arms etc are all fixed.
howard instruments are pretty good. also a place on maroondah highway as you head into ringwood - cant think of their name.

Is it a VDO gauge, Min & Max temp?

Its a smiths gauge I have found out with just max and min written on it. Not sure of what the working range resistance is.

Ordered one thru
http://www.howardinstuments.com.au
Very helpful people!

linky no worky
but this will
http://www.howardinstruments.com.au/