One day ahead, in microwaveable bowl, combine raisins, currants, peel, walnuts, prunes and cherries. Add 2/3 cup of the brown sugar, vanilla and almond extracts, nutmeg, cinnamon, ginger, allspice and cloves.
Stir in 1/2 cup of the rum. Cover and microwave at High for 10 minutes, stirring twice; let stand overnight. (Or, instead of cooking, let stand in a cool, dry place, stirring occasionally, for 3 weeks.).
Grease two 9 x 5 inch loaf pans; line with double thickness of waxed paper. Grease paper.
In large pan, bring fruit mixture and 1/2 cup water to boil. Reduce heat and simmer for 15 minutes, stirring often.
Meanwhile, in saucepan, bring granulated sugar and 2 tbsp water to boil over medium-high heat; reduce heat to medium and boil for 6 minutes or until thickened, brushing down pan with water to prevent crystals from forming. Pour over fruit mixture, stirring to coat; let cool.
In bowl, beat butter with remaining brown sugar; beat in eggs one at a time, beating well after each addition. Add fruit mixture, blending well.
Combine flour, baking powder and salt; fold into fruit mixture. Scrape into pans. Bake in 275F oven for 2 1/2 to 2 3/4 hours or until sides come away from pans and tester inserted in centers comes out slightly gooey.
Puncture each cake several times with skewer. Mix remaining rum with port; pour over cakes. Let cool in pans. Cover with foil; let stand for 3 days. (Cakes can be wrapped in plastic wrap and stored at room temperature or in refrigerator for up to 1 month.).