That engine block is basically the same from the first B, through the D15II. That includes the B,C,CA,D10,D12,D14,D15,D15II. Plus the forklift, and several other applications(power units, etc.)
The distributor drive housing bolts onto the block right in place of the magneto. The whole governor assembly is part of that system, and is changed with it.
Another possibility is the very popular aftermarket (Delco) dist. drive change over kit. It bolts right onto where the magneto is removed, and drives right off the original magneto drive/governor assembly gear, so it's simpler to install than the OEM dist. drive. Occasionally one will be for sale on e-bay, etc.