That is NOT going to give you an automatic choke Heater..and may mess with your oil pressure readings...
The sender works from ground reference, or resistance to ground.
There is NO usable Power there.
Even though you may read 12 volts at the wire with a meter, it has no usable current...It is a "Loaded Ground" when not hooked to the sender. and when hooked to the sender, you will see with a meter, it has no voltage..
At the sender , you are looking at power already being used by the gauge or light circuit, and going to ground. It's like hooking two 12 volt light bulbs in series to ground , If you remove the ground from the last bulb, you can read 12 volts at the first light bulb ground, until you hook up the second bulb to ground, then the 12 volts goes away.
You CAN hook it up to the sender by using a relay if you wish, just hook the relay coil to keyed power, and the ground side of the coil to the sender wire. The movable contact to the choke heater, and the stationary contact to 12 volts power.
The Stock version is through the Alternator Charge circuit. (usually the wire going to the Idiot light or gauge.)