Duster temp gauge problems

Hey guys, I posted a question about this issue before and am still having issues even after suggestions. I have a 1973 Plymouth duster with a 360 la motor and an aluminum edlebrock intake. My temp gauge needle does not move at all. I grounded lead wire that goes to the sensor and the gauge works and jumps up to full heat. I’ve checked voltage at the wire and it is good. I tried 3 different sensors and the third being an OEM but still after running engine for a long time the needle doesn’t move! This car is a new project and I’m still discovering a lot about it. I’m thinking if looking at the thermostat. This seems like a far stretch but if the thermostat was stuck open could the gauge always read cold and not move at all? Or if there was no thermostat in there could that also cause this ? The fan is not electric. I got an aluminum radiator too. Thanks!