The Rubber Floor Rug from GoWesty.com is a life saver.

For the first two years I had the van, I was constantly putting in new
measured carpet scraps.  In days they're trashed.  Even the dupont
stainmaster (YEAH RIGHT!).  But the rubber mats take a beating and just
need to be rinsed every once in a while.  The original rubber floor
mats are great too.

As for riding with the dog.  She kind of hates it unless she can have
her head near a window.  So the front seat is usually heres, with the
captains armrest down for her to perch on.  If I have a passenger, I
put the back seat down and open the back window.  She can't quite get
her head out, but I think she likes the wind in her face, as she
stretches to see outside.

As for a spill proof water bowl, we just buy the silver spill proof
ones with the rubber bottom.  They don't slip or spill, and you can get
them at just about every pet store.  Don't fill it too much, and you're
all set.  Besides, if it spills on a rubber rug, who cares?

About once a year I get the factory carpets professionally cleaned, and
they stay in good shape.

Oh - I also attach her leash to the passenger seat belt with a
carabiner.  Or to the front or back two loops, though I find I get more
tangles around the bumper that way.

-eric

PS - If you're in San Francisco - I'm the guy driving around the
Presidio with the black bumper sticker 'Lord Help Me To Be The Person
My Dog Thinks I Am.'

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'85 GL Camper (Moby)
San Francisco, CA