Hi Tim and welcome to the MOA,
As you say, in mast furling was definitely not standard on a Moody 28 and I doubt the value on yachts of this size. There are two ways it could have been converted from slab reefing to in mast:
The good way is to replace the mast with a purpose designed in mast furling mast, butthis isan expensive way to go
The economical way is to fit one of the rivet on after market product. While economical, this route increases weight aloft more than purpose built in mast systems and as the boat was not designed for this option, she doesn't have the ballast to manage it. By reputation these systems are ore liable to jams than a well maintained purpose designed in mast furling mast.
No furling system (roller genoa, in mast furling mains, in-boom furling mains) will work well if not given the benefit of regular servicing. This is not a requirement for engines alone but applies equally to the whole boat, including the rig. Blown out sails are also a common cause of jams on in mast furling systems.
Have you checked the boats for sale / wanted board on this site? It's currently listing 3 Moody 28's for sale:
Click on the type prefix to show just the ones you want to see
www.moodyowners.info
although one was posted in July last year and owners do not always remember to delete the post when their boat is sold.
Good luck with your search.
Peter.