|The change from the original hull and deck to what C&C called the Mk II hull and deck (which we call the Mk III and IV) primarily involved stretching the cockpit and bumping the hull at the waterline. However, if you crawl over the two boats, you'll see a myriad of small changes that could affect how the bulkheads fit, etc., where the chain-plates attach, how the bow is finished and so on. I'd want to take very careful measurements before even thinking about such a project.
If you don't mind, can you tell us why this project is gestating and how you come to have two boats to work with? And as usual, if the project does advance, we must have photos for Black Arts.
C&C 27 Mk IV