Sounds like they re-designed the keel at the factory using lead, steel, and plywood... I thought that your keel was originally like mine, i.e., a few wraps of polyester and glass over some big steel plates... and that your new keel was something you designed yourself. Either way, you did a great job, and your photos are informative.
I figured out the same thing with polyester vs epoxy. I started to do mine with cheaper poly, thinking this was essentially new construction, and started one side of the keel. It shrank and cracked after 24 hours, so I popped it off and re-did the thing with epoxy. (sailing small- sailboat restoration and repair
) Epoxy is not nearly as expensive as it used to be, at least from the smaller suppliers like Raka.
Keel construction and replacement is an interesting topic for me, since there are so many boats around with missing swing keels/daggerboards. And getting a factory replacement is often impossible, or more expensive than complete boats. It's a shame, really, 'cause these boats can be saved.
Author, Fix It And Sail, The Complete Trailer Sailer