In the bowl of a food processor, process vanilla wafers and pecans until finely ground. Set aside. (You may have to do this batches if you have a smaller food processor) *If you do not have a food processor, place them in a zip top bag and crush them with a rolling pin.
In a large bowl, sift together 1 cup powdered sugar, salt and allspice.
Add rum and corn syrup to the powdered sugar mixture, and stir to combine.
Add ground up vanilla wafers and pecans to the bowl. Use a sturdy rubber spatula or spoon to mix until fully combined and uniform.
Cover and chill in the refrigerator for 30 minutes. (Optional - I find it easier to scoop when the mixture has firmed up a bit)
Combine remaining 1/2 cup of powdered sugar and granulated sugar, if using, in a shallow bowl and set aside.
Scoop out tablespoon portions, roll into balls and toss to coat in sugar mixture.
Place on parchment lined baking sheet, cover with plastic wrap and refrigerate for at least 1 hour before serving.