I worked at a Hatteras dealer (not sales) and on the boats as crew when the 53 was common and newer. Hatteras was very high quality during that era, for example using a piano hinge instead of three smaller ones on a door, or using two struts instead of one on the shafts.
One thing you have probably considered are the Detroit Diesels. Much like having a slip, have a plan for Detroit Diesels. I read elsewhere that parts remain available; however, technicians are declining in number. Our most excellent diesel repair facility does not work on them, either. I am sure the Detroits can be kept running dependably for another 40 years, just be sure to have a plan for parts and a good wrench for when the time comes - or become the wrench yourself. This may become a bigger issue as time progresses, potentially impacting resale.
That said, I would very much enjoy owning a cherry 53ED with 8-71s! Better yet, a cherry LRC…
Good Luck