Mercury marquis needs rear end to get back on the road.

Wrecking yard is your best bet.

Parts unavailability is way I got rid of almost all my old cars years ago. You can comb salvage yards 'til you're blue in the face. But I'd rather have someone else do that. Visit local Ford, Mercury, or Marquis owners clubs. Those guys know everything. You could look at Hemmings or just google this... Who knows?

Try carpart.com and see what pops up. You can put your vehicle information and your location in the website and if any salvage yard, nationwide, has what you're looking for it will be listed on your search. For better luck you can select the other years and models option to include other vehicles that used the same part. For example, a Ford LTD or Lincoln Town Car of that era may have used the same rear. You can also try your local machine shop and see if your old one can be rebuilt. Good luck with your search! Jim