If your van is an automatic you might consider a kill switch to the Neutral Safety Switch wire near the emergency brake.  When the switch is activated the van can't be started but, unlike the fuel pump switch, if it is activated when the van is already running it will not cause it to die.  Something to consider.  There's a thread about this on Samba.  Good luck!
Stephen 

    On Wednesday, May 31, 2017 3:46 PM, Michael Magnani <mfmagnani@SBCGLOBAL.NET> wrote:
 

 Hi Chris,
I recently installed a switch that interrupts the electric fuel pump ground. Simple and works like a charm. Gives me some much needed peace of mind. 
Mike M

Sent from my iPhone

> On May 31, 2017, at 12:26 PM, Christophe Guilbert <cguilbert@PICASSO.UCSF.EDU> wrote:
> 
> Hi,
> 
> I often park my Vanagon (camper 1983 air-cooled) in an area with a lot's
> of homeless in SF. Some times, parts which are hard to find "disappear"
> on my van ! Well this is not life threatening and somehow homeless need
> to make a living !!! ;-)  What would really upset me however would be
> that someone steal my van !  I would like to install a killer switch
> which would make things harder to thief ! something smart requesting
> time to figure it out !
> 
> Any idea or experience ?
> 
> Thanks
> 
> 
> Chris