Our van is an 05 but we used the seat belt to secure it. If my memory serves me right, there are 2 ways to run the belt thru the carseat - an"longer" way and a "shorter" way. The instruction manual for the seat will clearly help you install it with the proper path.
Because the seat is so heavy, it took a lot of effort for me to get the seat in place. I climbed out of the back of the van feeling like I'd played a game of Twister.