As mentioned, need to pull the hub cap to determine if it is a FF or SF.
Re: determining FF by model/year, etc. - good luck. Ford often states that a particular model came with a FF as a stock specification. That is often enough not the case in reality.
Unless someone showed me the actual OEM VIN build sheet for the van, or a picture with the hub visible, I would not put any confidence in knowing what rear axle was present.
Beastie 3: 2002 7.3 EB Cargo: Agile TTB, CCV Mid Top, Custom Walk Through, Lots of stuff added. BlingMyRig.com