Geoff,

To remove them is simple - two screws on either side of pod, and then
slide to side, it will then come off its bracket which  will need to be
removed seperately.

As for opening them, I think they're glued (good luck!).  I would advise
against it.  Several reasons - 1 - two small for anything except maybe a
combined midrange/tweeter to be used in a 'component system' type
arrangement
2 - if your van is wired like my '85 was, you only have one lead going
to each channel positive and a common ground lead for both speakers.
Any hi-power amp or receiver wants a seperate ground (negative lead) to
each speaker.  I had to run a speperate wire to each speaker when I
upgraded the stereo in my '85.

You might want to consider mounting something else (and selling your
'pods' as people want them).  Note, later model vans (at least my '90
and '91) have seperate + and - leads to each speaker

Regards

Scott