Dissolve yeast in warm water in a large bowl, stirring well. Let stand 5 minutes or until bubbly. Add sunflower seeds, honey, bran, pumpkin seeds, oil, salt, and 4 cups flour; beat with a wooden spoon until smooth. Stir in enough remaining flour to make a soft dough.
Place dough in a greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until doubled in bulk.
Punch dough down; shape into a ball. Return to greased bowl; cover and repeat rising procedure 45 minutes. Punch dough down, and turn out onto a lightly floured surface. Let rest 10 minutes.
Divide dough in half, shaping each into a loaf. Place in 2 greased 8 1/2- x 4 1/2- x 3-inch loaf pans. Cover and repeat rising procedure 45 minutes. Bake at 350° for 35 minutes or until loaves sound hollow when tapped. Remove bread from pans immediately; cool on wire racks.