I finally moved up to 16 inch wheels a couple of years ago and wanted to have a spare tire mounted on a 16 wheel, as well. I had heard some conflicting stories about how to go about mounting this in the same place as the 15 inch spare: some said to just adjust the stock spare tire holder, others said you needed a new holder and some longer bolts - neither version mentioned cutting metal off of the van - which is what I needed to do! So here is how I did it.
As usual, your mileage may vary - this is how it was on my 95 - your van may be different!
I ordered a new bracket and bolts from GoWesty.
Not sure I would suggest doing that - you can get the bracket from the dealer for about $100 (at least a VW dealer in Seattle quoted me that price in 2018), and the longer bolts snd spacers did not work on my 95 - it may work on later models, and up to you to decide whether the spacers and bolts are worth it.
Here is the new backet, compared to the stock bracket - you can see the curve is more “generous” on the new bracket:
Here is the height of the 15 tire, and the 16 inch tire. There is almost 1.5 inches difference in the height of the tire.
Here is the room under the van to FIT the wheel/tire - the 16 inch would just NOT FIT!
So I used a multi-tool to cut away the bracket on the driver’s side:
I painted the cut edge, then used some edging to protect the tire from the cut area:
Here is the clearance with the 16 inch:
Here is the completed job - 16 inch hangs no lower than the 15 inch now!