Ok, well I can at least confirm for Hull #9, it was wood cored. Removed my aft/transom pump out port today in preparation for my diesel heater, which I plan to run the exhaust out the same spot. I’ve previously done the pump out relocation which as mentioned many times on here, is a must for early hulls.
One more piece of info sharing, I was worried about how to get the old pump out port to let lose from the hull. Ended up making my own tool to pull it. Used a piece of lumber, with a lug bolt run through it, and put the bolt through the port from the inside. Then on the outer transom had a drilled out board, and put the bolt through with a washer and nut on the outside. Then I added two small boards as spacers between the tightening board and the transom.
Sounds confusing, but here’s some pictures that will hopefully help. Anyway, it worked great.