Sprinkle pheasant cavity and outside with salt and pepper. Brown pork in a skillet .
Drain off any grease and discard. Mix pork with bread crumbs, beef gravy or brown sauce, and sage. Stuff birds with mixture. Truss the birds. Lay slices of bacon over breasts: tying in place if needed.
Place birds on a rack in a shallow roasting pan. Add 1/8 cup water. Cover ; roast 30 minutes at 350 degrees. Remove cover. Add chicken broth, celery, onion, carrot and allspice. Bake, uncovered, about 1 hour longer, or until tender. Baste frequently with liquid in pan.
To brown birds, remove bacon 10 minutes before end of roasting time.
Transfer birds to a warm platter and keep warm. Strain juices from roaster into a saucepan. Remove as much surface fat as possible; discard. Measure amount of liquid left. For each cup of liquid, combine 1 tablespoon all-purpose flour and 2 tablespoons water. Bring liquid to boil; stir in flour mixture. Continue stirring until thickened.