Rinse chickens. Season both the inside and outside of the chicken with salt and pepper. Place breast side down on racks in two roasting pans. Toss garlic heads in oil and place in the roasting pans. Roast the chicken and garlic in a 400 degree oven for 1 hour and 10 minutes. Cool. Separate garlic into cloves and squeeze pulp out of each clove into small bowl. Mash with a fork. Remove meat from chicken and dice. Discard skin and bones. Cover and refrigerate for up to three days.