Thanks for all the excellent info Frank.  I believe that the post about
diesel dipsticks that you refer to was mine.  The dipstick that I advocate
using is the one that comes installed by the factory on 1983 USA model
Vanagons and is available through the USA VW dealer network.  No
modifications are required.  1983 diesel Vanagons for the USA market all
have 5 speed transmissions, precluding the use of the 1982 style dipstick
system with the plastic filler tube.  Again, I have personally seen at least
2 different diameters of dipstick holes in the block, and currently have a
block with no hole at all.  If the engine block is compatible, this is a
much more accurate system of measuring oil level.

Mike Snow

<snip>
One listee commented about complete removal and replacement with the oil
dipstick tube used on the later diesels and turbo-diesels delivered other
than in the USA. This will work if carefully done. In my correspondence with
a German colleague, I was told that the bore in the block was different. So
I
did not investigate further. I saw one conversion where the owner cobbled up
the dipstick system from the later waterboxers and crafted a Swagelock
transfer between the WB parts and the I-4 dipstick tube. Bad. Had to
calibrate actual oil level to get proper stick length. Dipstick often caught
during insertion. ...
<snip>

Frank Grunthaner