Roadking53 lets start with some testing.
here is a write up i found a while back.
To your question yes the aluminum intake will provide plenty of ground (completed circuit) with the straps. Do not use any tape or pipe dope on sender.
see below for other items.
Power on the driver side of the gauge and wire to sender/sensor in engine on passenger side pin.
The temperature sender changes resistance as it warms up. When it's cold it has 500 Ohms resistance. When hot it has 50 ohms.
Gauge testing; When the sender/sensor wire is disconnected the needle should be below C. When sender/sensor shorted to ground the needle will go above H. if it always stays hot no matter what then there may be a chafe somewhere or the gauge is bad.
If you have an ohmmeter you can check the sender. Measure resistance with the engine cold and the gauge disconnected. Should be 500 ohms or greater. Start the engine and idle until warm. Resistance should go down to around 50 ohms or less.
If you have some resistors you could connect them between the gauge wire and ground to see how the gauge responds. Again, 500 ohms for cold and 50 for hot.
Measuring your gauge will also tell you how it scales for future adjustment.
Also try moving the wire harness with the key on to see if the gauge goes to H. Short testing
IMPORTANT: The original gauge calibration puts the temp gauge near the center of the range around 170 to 180 degrees. Running a 190 thermostat usually causes the needle to rest much closer to "hot." If your engine is averaging 195-205 that's going to put the needle at "Hot." Aka the LS guys get burned on this one because they think its hot when its not.
You can add a resister in line to scale it appropriately for your setup.
