68 Barracuda........ Temp and Gas Gauge Issue.

Do the above, but do it just for a few seconds to avoid burning out the gauges.

Better yet, order a 10 ohm, 1 watt resistor from www.mouser.com and put that between the temp sensor wire and ground, and then between the fuel sender wire and ground, and see if the respective gauges move to approximately full scale.

You are making progress!