Melt the 1/2 cup of white chocolate chips in a double boiler over medium-low heat or in the microwave for about 1 minutes. Stir often to keep the chocolate from burning. Transfer to a large bowl. Add gingersnap crumbs, pumpkin, graham cracker crumbs, sugar, zest, cinnamon, salt and cream cheese and beat with an electric mixer until smooth. Transfer to a shallow bowl, cover and chill until just solid enough to roll into balls, about 2 hours.
Line a large sheet tray with parchment paper. Melt remaining 2 cups white chocolate almond bark and transfer to a small, deep bowl. Roll 1 heaping teaspoon of the pumpkin mixture into a ball in your hands, then drop into the chocolate. Working quickly, gently spoon chocolate over to coat. Using a small spoon or fork, lift the truffle out of the chocolate, shake off excess and transfer to prepared sheet tray. Dollop a bit of extra chocolate on any parts that remain exposed, then sprinkle a few gingersnap or graham cracker crumbs over the top, if you like.
Repeat process with remaining pumpkin mixture and chocolate, then chill truffles until chocolate is completely set, about 1 hour.