Older Rhodes 19 questions

Dec 4, 2016
10
Rhoded Rhodes 19 keel Bar Harbor
I have an early R19 keelboat that appears to have never had ribs or floorboards - would it have been possible to buy one New without them? The tiny builders plaque has the numbers: 2 63 on it - would this be the month and year built or the hull #, or what?
Do I need to install the optional foam floor timbers to make the boat unsinkable or will the oak timbers suffice? Many thanks!