You decide what a listing is. Add your own fields to companies: a yes or no badge like "accepting new patients", a multi select like "chamber member", a category, opening hours, whatever your market cares about. Everything downstream follows on its own: the public listing card, the filters, the category pages, search, and the form a business fills in to get listed.
Charge for listings. Set up tiers so a business can pay to be listed or to be featured, sold the same way as your job posts.
Import the list you already have. Upload a spreadsheet and see exactly which column became which field, how many rows came through and what we could not place, before a single row is saved. An import that quietly guesses wrong across four hundred businesses is worse than no import.
Companies is now a full workspace and it is where you work through your listings. Open one to read and edit its details, the people you know there, your notes and history with them, their jobs, and what they have paid you, all in the one panel.
Fill a company in from its website instead of typing it out, and merge duplicates so one business is one listing with all its jobs attached.
Switch it on when you want it. Boards running a directory get their own section in the sidebar. Boards that do not are unaffected.