The DCD is a very old design. I think it first came out in the late 50s. This is not to say it is no good. It was standard equipment on the Ford Cortina GT and several models of Fiat in the early 60s. It is a very versatile carburetor, adaptable to engines of widely varying sizes. Not only are the jets changeable, but the venturies are as well. There are also emulsion tubes that come in various sizes.

If the one for sale that you are looking at comes with a manifold for Volvo B18/B20, the jets and venturies may be close to what you will need. Otherwise you will have to find out what the correct parts are for your application and obtain them.

A peculiarity of the DCD is that is doesn't have a proper choke mechanism. Instead, it uses an enrichment device or "starting carburetor" that adds extra fuel when the knob is pulled. This doesn't work as well as a real choke when the weather is really cold (-5 C or colder)

Most Weber conversions I have seen use a DGV carburetor, which has a normal choke butterfly, that can on some models be operated manually, or is automatic, either by water temperature or an electric device.