In case it helps with your future purchase:
Back in August 2006 I bought an '81 Joker, 1.9 Petrol, Westfalia High Top conversion. It is a German import, LHD and ALL its bits are standard. as soon as I had the engine started I knew I was In love again. Tis that sounds you see, not scared to see it actually makes me a bit horny
TIPS WHEN BUYING
-Do take somebody knowledgeable with you when buying the first time.
-Get the seller to show you the engine bay.
-Check the engine is cold, if it is ask the engine to be started while you check for (blue) exhaust fumes. Put your hand in front of the exhaust, what does it smell of? Traces of anything? It is normal for Aircooled engines to use a bit of oil.
-Do check for rust, feel the surface, give a knock on things you are not sure of. remeber the van is made of metal sheets so the sounds is distinct.
-Get the van on a ramp!
-If you can, get an oil pressure and a cylinder pressure test done or ask for the results. Get this checked against the values in the Haynes manual.
-Drive the van, make sure you go faster than 40mph and test brakes, gear shifting, acceleration, steering. This is a big commitment from the seller's part so be ready to read into his answer when prompted.
-Put money aside for any eventualities.
-Don't buy without seeing the vehicule, nerver
-Don't buy in haste
-Don't pay over the odds.
Additional stuff
FUEL ECONOMY
I have just been driving for about 2 weeks around the UK (from the South East to Yorkshre Dales, Cumbria, Bath and back. Beautiful country this is!) and have had an average of 26MPG (that was with camping gear, 25litres of water in the tank, suitcases, fridge filled up, cupboards filled with food,...).
On Motorway I did a healthy 100kph (+/- 60MPH), but this would drop to 80 kph (=50MPH) when going uphill. This would return me up to 32MPG.
It is a Classic car, so if you drive it like one you will get even better results. (I don't think in terms of acceleration but in terms of 'avoid havin to brake')
Lower your time-machine and you will get even better results. If you add a gas conversion, you will, for the same £50, be able to fill her up twice. Effectively you double your MPG value, so +50MPG is not impossible.
BRAKES
Brakes are not as strong as current vehicules so leave plenty of room, look ahead and try not to lose it when a little dickie cuts you off just in order to get in front of you at the stop light)
MAINTENANCE
Replace the oil and filter every 5k kilometres or 3k miles. (max £70). This is the best way to keep your engine going for another 30 years.
I dont actually have a lot to say here, these things dont seem to go wrong a lot.

It is possible to get the engine overhauled, mine has done 230k kilometres and so far NOTHING needs replacing. Carbs are on their way out though.
Good luck