I have been around Fords my whole life and with all the stuff I've read and heard, I have never heard of a "high port" cylinder head being put on stock 351s. Are you talking about GT-40P heads. Because I know with them you need custom headers and spark plugs. They may have put these heads on late model performance or heavy duty 351s. I've built 3 sets of 351 heads from 69, 74, 78 and they all were the same port location, nor have i ever read of any or seen any for sale. Trick Flow makes aluminum "high port" heads for racing but they didn't come on stock 351s from the factory, and with these you also need custom headers.
1975 to 1984 ford small blocks (302&351) are the ones to avoid for big performance build ups. They are thinner castings and will not put up with as much as the earlier and later ones. The upside is that they are lighter though.