Gauges

So I’m having a interesting gauge issue in my 71 Dart. When I turn the key to run my aftermarket tach/stock temp/fuel gauge all turn on, but when I start the car and it’s run all three don’t work. Only thing I have done recently is change my power steering pump and fuel sending unit back to the stock one so it would read the tank better. I’ve grounded the sending unit and even gone back and cleaned up where the ground strap attaches to make sure it’s metal contact. Other than that this hasn’t been an issue. Sometimes the tach wouldn’t work, but I could just turn the car off and turn it right back on and it would be fine. Any suggestions on what my issue is? Or at least some where to start looking? I’m thinking it could be a ground for the instrument cluster but where is the ground for it? Only ground I know of in the car is the steering column. As always thank you for the help!