Brakes losing pressure at red lights, any ideas?

Great info 67dart273!! It helps a lot! I've done wheel cylinders, shoes and pads, hoses, now the proportioning valve...but never had a M/C off before.

I'm looking around online now at M/C's. Probably go with Rockauto? They list a new one for the 73 Dart for front disc and rear drums.

I'll draw it out as you per your instructions and let you know if I have any questions.

Now's the best time to do this...my wife is often with me when out driving around.