What can I swap, 85 cop Gran Fury to 71 valiant

The front brakes will work if you have the large upper ball joint, or a spacer for the little one. Use the entire spindle. The cop cars have larger diameter caliper pistons too. The rear axle will be a little wide but might have a sure grip. It will be a roller block but it may or may not have the roller cam installed. Should have 360 heads. Power steering box will work, but maybe not the drag link.