re: "The only way to insall new push rod tubes, (original,
style) is to remove the head."

This may be correct (I don't actually know) for earlier
aircooled VW motors but not for the TYPE IV used in
Vanagons.  I've replaced the seals on my 81's pushrod tubes
at least twice and have not removed the heads.  You do have
to remove the rocker assemblies, and boy are those lifters
noisy when restarting!  The Bentley manual is pretty vague
here, but here is a direct quote from Haynes:  "With new
seals in place over the pushrod guide tubes, fit the tubes
through the holes in the cylinder head."  There is no need
for expandable tubes on TYPE IV engines.  John must have
some obstruction, probably deposits, preventing his
reinstalling the tubes--never had any problem myself.