Bring A Trailer is one option, though I'm sure fellow members will give you mixed feedback. I sold my BMW CS with 1600 Veloce (North Salem, NY) in 2022 and was very satisfied with the result. They handled all prep work (detailing, photography, driving videos) and did an excellent job marketing the car online as well as at local car events. They capably took care of all of the Q&A, often populated by all-knowing (but not bidding) pundits. The commission was reasonable for the prep effort. Having a high-volume BaT dealer like 1600 Veloce handle the sale usually gets the listing online quicker, but I have heard others who have listed cars on their own report that the turnaround time from initial contact to online listing can be quite quick. Keys to BaT success are anticipating typical W113 questions (ie, fender notches, fender spot welds, maintenance records) along with detailed photography and videos -- reviewing a few listings will tell you what you have to expect in terms of questions.
There are other options (ie, traditional auctions, Hemmings, MB Market etc), but no one else comes remotely close to BaT's scale and reach.
