Ted pretty well covered it. I will add that the Kadron VW dual carb kit has been around since at least the early '70's (I saw my first set in '74 and bought a set a year later). They are a decent carburetor set up, simple to install and tune, and a part of a lot of people's introduction to VW high performance. If buying a set (especially used), one should figure getting the throttle shafts machined for bushings, as even new carbs can leak. Jeff at Kaddie Shack (advertises on the Samba) provides this service and seems to have a good turn around time and good customer service. Low Bugget (AJ Simms) also specializes in kadrons (including modifying them for much larger motors), but has a reputation for horrible customer service, as evidenced by the Samba thread in the Samba Feedback Forum. They are fairly versatile and work well on stock 1500's (with single port manifolds) as well as larger motors up to about 2 liters, the caveat being the 28mm venturis they come with may restrict power on a larger motor if too much duration and headwork is used. There are larger venturis available and even larger throttle bodies and high-flow air cleaner mounts (which all work), but at this point it may be better to spend your money on some Webers or Dellortos, as a new set modified to run on a larger than 2 liter that goes to 6 or 7000rpm costs over $700.