Winstar 2001: should the back bench be adjustable?

I bought my winstar from a used car dealer with no back bench. So the dealer order a matching bench. but I notice that that you can't adjust it forward or backward, like other winstars I have seen at the dealers. Do all winstars sports model 2001 have an adjustable bench? I called a few local dealer to ask that question, but each one I talk to tells me something different. Maybe the bench I have, is supposed to be a middle bench and not for the back? (from Canada, Ontario). thanks.