Update on a couple of things I forgot or didn't admit to.
Tried to use a hand impact wrench with both the 6mm allen in a socket 
and with the 6.2mm (1/4") also.  No luck.  Tried driving a 8mm 
12 point into the hex, no luck either, just ended up rounding a couple 
of teeth on the 12 point.  Boot is already cut off for access.

As to suggestions, thanks for the ideas.
Welding on somthing sounds good, but no welder.  Vice grips: can't 
see how to get a good grip with the limited space INSIDE the Vanagon 
style rear end housing.  Pounding face of bolt head to deform to 
shrink size of hex is good, and well worth a try tonight.

Again, respond to type 2 list, you Vanagoneers!

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