I am looking to make a list of current day surnames where my ancestors lived in the 19th century to aid in translating and spelling out names in old baptism and marriage records. I know that the German phone book exists, but can't seem to find a way to get a full list of people in a zip code. The area is Billigheim, in Baden-Württemberg.
This is not a direct answer to the question, rather a different approach to (I think) meet the same end.
The problem with using a list of current day surnames for this purpose is that there are probably very few similarities between the modern surname distribution and the 18th or 19th century distribution.
One thing you could do is use a FamilySearch database to generate a list of surnames. For example, I selected Germany Births and Baptisms, 1558-1898. If you search this database only entering the birth place as "Billigheim" and restricting it to a decade, say 1710-1720, you will get about 820 results. If you are logged into FamilySearch with a free account, you have the option of exporting the results to a spreadsheet:
You can only export up to 75 records at a time, so you would need to do it about 11 times to export all those records from that search, but it does not take long. Once you have all the records in one spreadsheet, you can use an Excel function to extract all the surname fields, and then remove all the duplicates. The most common surnames or spellings will appear multiple times of course.
This is not perfect because there will be transcription errors, but even so I think you would get a more useful database of contemporary surnames to aid with your transcription and interpretation of names.