best place to add water temp sending unit for aftermarket gauge?

[wdrlaw]

Only 05/06 crossover has the driver side plug (Used to vent the radiator) 07/09 does not have the plug.

I mean the plug below the exhaust header on the driver side, sorry.

 

[JC SSP]

Old trick when tapping oil pans is using thick coat of axle grease. That usually catches most metal filings.