Dave ...
From what I've been told by a few early CV16 owners, the deck is glassed to the hull and not just tabbed in a few spots like the newer CV's, by newer I mean (1974 models) with the hump by the wind shield bar.
PLUS the deck and rub rail were riveted to the hull, newer one had screws for deck and rub rail ...
I would bet the PO cut out the back of the splash well, dug out the old transom wood, replaced with new and glassed the splash well back on, which is why it's white/orange and no skid back there ...
Piece he cut to access transom wood ...
As you can see from above picture the cracks in your splash well might just be from the repair work ...
And not a bad transom ...
I have a plate on mine to cover old Merc mounting scars ...