First off what air filter is fitted? Ideally you want a stock one with the hot air feed. There should be a cardboard tube running to it. If its a pancake type filter you will get problems with carb icing that will lead to cutting out at idle. Carb icing tends not to happen on twin carbs due to the shorter manifold length.
Secondly, its worth doing a basic service so plugs, HT leads, dizzy cap, rotor arm, points and condenser. It's also worth changing the oil (in the air filter as well if its a stock oil bath type) and the rubber fuel lines (and in-line fuel filter if fitted)
After you have changed the points you will need to reset the timing, you can time it statically but ideally its best to get a timing gun.
You can check the rubber boots on the carb manifold for leaks by spraying them with WD40 when the engine is running. If there is a change in RPM then there is an air leak and a new boot is needed.
After that its worth looking at the carb, its worth trying to set it up first rather than pulling it all to bits straight away.
Is there any leaks/wetness from the spindle which the thottle lever pivots on. Remember to check both sides.
Also are there any open outlets on the carb? For example if a 009 distributor is fitted you need to block off the outlet on the carb where the stock distributor would take its vacuum from.
If the van takes more than a couple of turns to fire after it cuts out you may want to remove the top of the carb (the five flat head screws) and check the float bowl is full of fuel.
Here is a tuning guide http://www.vw-resource.com/34pict3.html" onclick="window.open(this.href);return false;
If it still won't play ball its worth ordering a rebuild it and stripping and cleaning the carb. Again there is a guide on the link above.
