To make the crust, in a bowl, stir together the crushed ginger-snaps and butter until the crumbs are evenly moistened. Transfer the crumbs to a 9-by-2 1/2-inch (23-by-6-cm) springform pan and press evenly onto the bottom and 1 inch (2.5) up the sides to form a thin, even crust. Refrigerate for 30 minutes.
Preheat the oven to 350°F (180°C). Put the raisins in a small saucepan, add the rum, and heat over medium heat until the raisins are plump and soft, about 10 minutes. Remove from the heat and set aside.
In a bowl, using an electric mixer on medium speed, beat the cream cheese until smooth. Add 3/4 cup (6oz/185g) of the sugar and 1 teaspoon of the vanilla and beat until blended. Add the eggs one at a time, beating just until smooth after each addition and stopping to scrape down the sides and along the bottom of the bowl so that the ingredients are thoroughly mixed. Add the raisins and rum and orange zest and beat just until well mixed. Pour the filling into the prepared crust. Bake until firm, 50-60 minutes. Remove the cheesecake from the oven and immediately place in the refrigerator on a kitchen towel to chill for 15 minutes. Raise the oven temperature to 450°F (230°C).
In a bowl, stir together the sour cream, the remaining 1/4 cup (2oz/65g) sugar, and the remaining 2 teaspoons vanilla. Remove the cheesecake from the refrigerator, pour the sour cream mixture over the top, and return the cheesecake to the oven to bake for 10 minutes. Transfer to a wire rack and let cool completely, then cover and refrigerate until well chilled, at least 24 hours or for up to 3 days. To serve, release the sides of the springform pan and lift off; leave the cake on the pan bottom. Transfer the cake to a serving plate. Serve cold or at room temperature.