1969 Dodge Dart Gt temp gauge and fuel gauge not woriking

Since you didn't mention an OIL gauge I'll assume you dont have one. In that case there is a voltage limiter plugged into the back of your panel that could be the problem.
As stated before ground the sender wire at your temp sender and turn the switch on. That gauge needle should travel rapidly to extreme hot. Dont leave it there ! Turn the switch off. Replace the sender. If the needle doesn't move, replace the limiter on the istrument panel.
Keep in mind that the new limiter wont work without a chassis ground. If you want to turn it on and test it before completing the panel install you will need to attach a temporary ground jumper.