We have a '90 Westy based on a Vanagon GL. The GL's were tricked out with a number of options (not all GL's have all of the toys, though), including air conditioning. The system was designed to operate with R-12 refrigerant. R-12 is nasty stuff that does ugly things to the environment. It is taxed to death (by intent) if you can even find some. Another refrigerant, R-134A, was created to take R-12's place. The good news is it's not so nasty, the bad news is it's not as efficient as R-12. That means that you simply won't get as much cooling with R-134A as R-12 delivered. But! There is another option: Red Tek (www.redtek.com of course). This is a petroleum-based refrigerant that is much less of an environmental problem than R-134A. Better still, it's much more efficient than R-134A. But... most a/c shops won't touch it for a very good reason: they don't want to mix it with their R-134A equipment. But! Harbor Freight is your friend. Get their gauge set (every a/c tech has one) and their one-stage vacuum pump, some cans of Red Tek, and you're good to go. How to do the installation is a topic for another thread, but it's really not hard to do.
So, yes, there is factory air conditioning. Using Red Tek, I'm currently getting air out of the vents at about 40F when the outside air temperature is around 80F. A 40F temperature differential's not too shabby.
DISCLAIMER: I have no connection with Red Tek (or VW) save as a consumer.