Preheat the oven to 375°. In a small bowl, mix the first 4 ingredients. In a large bowl, whisk the eggs. Whisk in the pumpkin, evaporated milk, and the sugar-and-spice mixture; pour into the piecrust. Bake until just set in the center, about 1 hour; let cool completely on a wire rack.
In a medium bowl, whisk heavy cream, bourbon, and confectioners' sugar until soft peaks form. Top the cooled pie with the bourbon whipped cream; drizzle with more molasses.
