Combine pecans, almonds and walnuts in food processor. Pulse nuts until they are slightly grounded (you don't want to emulsify them). Add raisins and pulse for 20 seconds. Transfer mixture to large mixing bowl. Stir in all remaining ingredients. Place stuffing onto dehydrator trays and dehydrate at 90°F for 12 hours or until dry. Serve stuffing warm from dehydrator with gravy. Stuffing mixture can also be made in advance. It stores for up to 3 days in the refrigerator prior to dehydration, and up to two weeks after dehydration.