Assume you are aware of this site from 2012
sites.google.com/site/ss39australia/The site is a bit unfinished - it is obviously one of the free website types and only the Home page works but the links to boats there has some information about 4 boats. They might still be contactable for information.
As per Chris's post;
1 Michael Spies would presumably be able to provide information from the Mark Twain restoration effort.
www.sail-world.com/news/212912/Its-all-about-the-training2 and it would be good to check your rig size so that it would match your cut down keel size etc.............or not.
Assume you have the details of how the keel was lengthened so that you can reverse the engineering involved in this and get back to the original keel without jeopardising the whole keel's structural integrity under all the keel design load cases including full lateral capsize to 90deg heel and sand back grounding at some speed. Keel lengthening projects must be very rare? And keel unlengthening projects even rarer? Assume you have your reasons.