Thanks to all for the suggestions and ideas.  Finally got it off. 
Here's the saga.  On the way home purchased a NEW 5" pair of 
Vice Grips, the real brand, to go with the 5 pairs of bigger ones I 
already have (Wow, I didn't know I had that many, musta been breedin')
Found a 7mm allen wrench, and bought another 6mm while I was at it.
Couldn't find Liquid Wrench in a spray to get behind the axle.
I have already removed the rubber boot to verify it's really a hex 
I'm messing with and cleaned it well with dental tool and carb 
cleaner.  Bolt in question is fortunately in the full down position.  
Inner bolts all removed and CV is wired in the full up position.

Cut off the 7mm with a cutting wheel on a drill (resin and fibre 
style wheel) and ground a slight taper on the hex.  Installed hex 
into bolt, smacked it and attempt to loosen, (many times did I 
do this) to no avail, got it seated well, but it cammed out each 
time.  Even used the impact wrench.

Stared at the already removed CV joint stuff and realized that the 
thin metal portion of the rubber boot is what was in the way of 
access by the Vice Grips.  Found my largest, lifetime warranty, 
screw-pry-cut-bend-driver and placing it upon the offending piece of 
metal drove the tool through the metal in a few places with a heavy 
heart, I mean hammer.  Felt good.  Then applying same tool to center 
of cut pieces proceeded to bend them towards the center of the hub.  
This provided clearance to allow Vice Grips to be in positon to grip 
on bolt head.  FWIW there is sufficient clearance to get a 7in pair in 
there, but I haven't the hand muscles to squeeze the pliers 
sufficiently to grip bolt head enough to work, bummer.  Same with 5in.

Confident now that there is clearance for Vice Grips, I gave up and 
drilled that head off.  I happen to have a few carbide oval shaped 
metal removing tools, and used them instead of a drill bit.  Removed 
the head and removed CV.  Applied Liquid Wrench to threads, and 
applied 5in VG's, but wasn't necessary 'cause by this point that bolt 
was finger loose.

So the moral of the story of CV bolt removal in a Vanagon.  Drilling 
out the head is fairly easy and once done and CV removed, access for 
liquid bolt looseners and VG's is available.

Now to install the temporary pair of CV's until the new ones arrive.

- Jeff + (2) '80 Westi's, '67 Sqbk, '64 Ford Crewcab, '87 Subaru 4WD
Grass Valley, California, USA, Earth