CRUST:
1.  Melt the margarine and mix with the cracker crumbs and sugar, making the crumbs evenly moist.  Press the crumbs into the bottom of a 9 x 13 inch baking pan and bake at 350 degrees for 7 minutes.

FILLING:
2.  In a saucepan, heat the pumpkin, brown sugar and spices over medium-high heat until the mixture becomes bubbly.

3.  Beat the eggs, then slowly add the pumpkin mixture.  Beat in the cream cheese last and pour over the hot crust.  Bake at 350 degrees for 35-45 minutes or until the center is set.

TOPPING:
4.  Mix sour cream with brown sugar and vanilla and spread over the top of the cheesecake.  Return to the oven and bake for 10 minutes or until the topping is set.  Cool cheesecake to room temperature, then refrigerate.