Melt 1/2 cup chocolate in a double boiler over medium-low heat or in the microwave for about a minute. Stir often to keep the chocolate from burning. Transfer to a large bowl and add gingersnap crumbs, pumpkin, graham cracker crumbs, sugar, zest, salt and cream cheese. Beat with electric mixer until smooth. Transfer to a sallow 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 chocolate and put in small, deep bowl. Roll 1 heaping teaspoon of pumpkin mixture into a ball in your hands, then drop it into chocolate. Working quickly, gently spoon chocolate over to coat. Using a small spoon or fork, lift truffle out of chocolate and transfer to prepared sheet tray. Dollop a bit of extra chocolate on any parts that remain exposed.
Then sprinkle with gingersnap or graham cracker crumbs over top. Repeat process with remaining pumpkin mixture and chocolate and chill for at least 1 hour