4 wheel disc on 74 Duster - Prop valve?

I am working on getting my car driving after 4 years... Down to the last few items.

The car had front disc and rear drums stock. I upgraded to 11 3/4 up front using Cordoba rotors and mount. I bought a kit off of ebay for the rear. It is all hooked up. I finally started the car up today, had it up on jack stands and shifted into gear. The rear keeps going unless I mash the brakes all the way to the floor. And even then, doesn't want to stop. I think I need to adjust the rear calipers a bit. There is some adjustment. But I noticed my prop valve is leaking... So another thing to replace.

Any recommendations? Should I upgrade to something else? I did a little research using the search function. But mostly lots of opinions. I am looking for someone else running 4 wheel disc brakes for what they are using.

Any help is appreciated. The old car is finally ready to drive. Excited and nervous at the same time...