I don't know if there's any solid numbers on this. My personal observation has been that about half of the '51s produced did not have a deck lid. Most '52 and '53s do. As noted in a discussion on here last fall, the '52-'54 Corsairs were available without a deck lid but the Corsair Deluxe had a deck lid. Even given that info, very few of the Corsairs didn't have a deck lid. In fact, the first time I saw a '53 Corsair without a deck lid was 10 years ago and I've been messing with Henry Js my whole life. Contrary to popular myth, many '51 four cylinders have a trunk lid and a lot of '51 four cylinders have both a trunk lid and folding rear seat.