It's a good idea. I usually do triple gauges in my car, oil, water, volts. There is a plug down by the oil filter in the 5.0 cars, probably the same place on the 4.6 as well. I haven't put any in the GT yet, so I don't know for sure.
My last gt had 10 pounds of oil pressure at idle but showed great oil pressure. That's when I figured that switch was a dummy. I'm wanting to put oil pressure. Air fuel. And ... I don't know a good third one