Sorry to disappoint you, but they are spot welded welded in.
Actually it's not too bad to do. I found a lot of the info needed on the Forum (loads there if you search).
Mine had the half height one welded in and the top half was bolted. I unbolted that and Mark4 gave me a generous amount of van tokens and installed it his work and play project.
To remove the lower half welded in bulkhead, I removed the seats and disconnected the seat belts at the bottom. This will then give you working space. I then used a spot weld removing drill to drill into the spot welds (making sure you don't drill right through and into the fuel tank!), then I used the angle grinder, club hammer and bolster. When using the angle grinder, make sure you have something to stop the sparks hitting any of the glass (I used a large piece of cardboard and a dust sheet)
All in took me about 2 1/2 hours on my own from start (taking the seats out) to finish (touching up the metalwork with a rattle can, putting both the seats back in and bolting back both seat belts).
Enjoy your van, and have fun taking out the bulkhead
I have just took the top half of my factory bulkhead out.. After reading a lot of posts on the subject.. I found the best way for me was to cut out the top and bottom with a grinder and them thin discs(i used 4 of them) and then gotta sharp metal chisel and hammer to he side welds and the ones in the top corners.... Word of warning though!!! remove the plastic seatbelt covers from the top and i duck taped all around from inside the cab to make sure no grinds went into the cab itself....