Why don't you contact Hans Geissler, the designer and builder of the G-Cats? Even though he is not actively building new boats right now, he told me he has lots of parts. And, of course, he should be able to give you the lengths and dimensions of everything you need to replace.
His website is at
http://www.geocities.com/g_catmultihulls/misc/maytheforcebewithyou.htmlYou can find further contact information there.
