I have mine currently in the top of the housing. I feel that it responds veryslowy and detects more heatsoak. If you want to do it properly; drill and tap right in font of the themostat. Responds faster and more accurate. My 0.02

 

One drawback from this location is that it is on the radiator side of the thermostat, as opposed to the engine block side.
This location will not read temp until the thermostat opens letting warm/hot coolant out of the engine block. While it will still be an accurate reading once the thermostat opens I always have nagging feeling of what if the thermostat doesn't open?
All in all I still feel that this is the easiest way to hook a sender up, but others have tapped into the throttle body coolant line with success too. To each their own.

Regards,
Frank

 

the VDO gauges that match the FD interior perfectly are the vision series. I have the boost gauge and just picked up the water temp gauge and will be installing soon, but was recommended to install with a brass T in the throttle body coolant line.