Hi Dan,

I have what sounds like the same leak as you, around the clutch pedal.

Along the lines of what Ben said, I thought another common cause for
leaks is a wearing out of the sealant between body panels.  I've been
assuming mine is coming through that vertical seam running down the
"nose" of the vanagon just inboard of the radio antenna.  My sealant
there is clearly worn out (hard/cracked/missing).  Admittedly, I have
not confirmed this source, as the van doesn't see a lot of rain, and
I'm hoping to get a paint job in the next year or so, but it might be
worth a look or hose spray.

Good luck,

Alex