The vents were put in to ventilate the bilge on early boats - they were removed on later boats that had the gas tank in its own tub so gas (supposedly) could not leak into the bilge.
Hi ace3,I can probably get you a vent made for $75-$100, the only reason for the price "range" is what we have to pay for the teak plank, we usually have to purchase more than we actually need. Let me know if you are interested. I can send you a pic of mine installed on my 73`. They do look very nice.