Hold up there. The vin numbers are in two locations on the van. The easiest place is the back cross braces in front of the taillights. Either on the left or right. Usually the right has the vin # stamped into the metal of the brace. The other location is the floor under the lip of the doghouse. Usually on the right side. This requires unbolting the doghouse from the floor and cleaning the seal that glues it to the floor.
It is stamped into the sheetmetal of the lip.
Those are the permanent locations of the serial vin numbers. There are door tags, but the problem is they get removed or the door gets changed.
Guys have 61 econo van, but the door has been changed with a door from a 67 with 67 tag on it. Then the van gets sold as a 67 not a 61.
Check those other location first if you do not have a door tag.