BEAT pumpkin, pudding mixes and spices in medium bowl with whisk until blended. Gradually add milk, mixing well after each addition. Stir in 1-1/2 cups COOL WHIP. Spread onto bottom of crust.
TOP with marshmallows and nuts; drizzle with syrup.
REFRIGERATE 1 hour or until firm. Serve topped with remaining COOL WHIP.