1973 Dart brake failiure

Hey, im abit confused here, I was under the consensus that the brake lines (or atleast the connectors for this car was supposed to be two different sizes, with the front line being slightly bigger, I just went to start trying to pop the lines off the installed one and the nuts for the lines are both 9/16th? The replacement i have definitely doesn't seem to have two of the same size outlets as the two bleeder plugs are different thread sizes, looks like 9/16th and 1/2? Are the nuts the same size for a different size thread bt chance? Or am I just mistaken over the size I need.