Soak corn husks in hot water to cover 30 minutes. Separate husks, and continue soaking 30 more minutes. Drain husks, and pat dry. Tear 4 smallest husks into 14 strips.
Beat shortening at medium speed with a heavy-duty electric stand mixer 2 minutes. Combine masa and next 4 ingredients. Gradually beat masa mixture into shortening. Beat shortening mixture 2 minutes, scraping down sides of bowl as needed.
Gradually add warm milk to shortening mixture, beating at medium speed just until blended and scraping down sides as needed. Add pumpkin, and beat at medium speed 3 minutes. Cover dough with plastic wrap.
Using hands lightly coated with masa mix, spread about 2 Tbsp. dough into a 3- x 4-inch rectangle on right side of 1 husk, leaving a 1/2-inch border on right side and a 2-inch border from narrow bottom end of husk.
Spoon about 1 Tbsp. pineapple down center of dough. Sprinkle with about 1 1/2 tsp. raisins. Roll up husk, rolling left side over right, enclosing pineapple mixture and raisins completely in dough. Fold bottom narrow end up and over, and secure with husk strips or kitchen string. Repeat procedure with remaining corn husks, dough, pineapple, and raisins.
Place 2 tamales side by side, seam sides inward and open ends facing same direction. Tie tamales together with kitchen string, securing bundles at top above dough. Repeat procedure with remaining tamales.
Arrange tamale bundles, open ends up, in a steamer basket over boiling water in a large Dutch oven. Cover and steam 35 minutes, adding more boiling water as needed. Remove tamales from Dutch oven, and let stand 5 minutes. Serve with Vanilla Sauce and Mexican Chocolate Sauce.
Note: For testing purposes only, we used Masa Brosa Harina de Maiz Instant Corn Masa.