73 duster front brakes locking up when coming to a stop.

flathead31coupe said
So after looking at diagrams for the master cell or to the proportioning valve. It looks like the rear master cylinder port , which is the front brakes go to the top of the proportioning valve , is that correct

Post a pic of it. Easy to tell the difference between the drum/drum and drum/disc.

And, yes verify that it is plumped correctly, namely that the line for the rear comes out at the bottom rear port.