I have a copy of the owners manual for that vintage 23, but it says zip about the sink! I'm not sure if Rudy at D&R would have a manual, but even if he doesn't..he will have more info than any manual would list! My manual is for the pop-top 23, but except for the pop-top, the 2 versions of the 1970-72 23 were the same (well ,the non-pop-top had a hinged mast instead of the pop-top's thru-deck stepped mast).
The sink drain for those early 23s was lead to a thru-hull and the drain for the icebox was tee'd into the hose as well.
As Joe says, the CB should be lowered for sailing, but you will be able to sail without the CB if it is stuck. The keel is cast-iron the Cb is hollow fiberglass with 20# of lead flashing inside for ballast.
I've included a copy of the manual....sorry it isn't a real clear copy..