I think the little Airfix kit may have been issued in full-hull form before. That nice little stand looks familiar. I have no idea whether the waterline version or the full-hull version came first. The first one I bought was the waterline version, but one or both probably had been on the market for some years before that.
I see the old paper flags and transom are still there - though on a separate sheet, rather than the instruction sheet. But the "shrouds and ratlines" printed on clear plastic are gone. That's a shame. It really wasn't such a bad idea.
I think the first large Airfix Victory I bought (somewhere around 1968 or 1969) was in an "Airfix by Craftmaster" box and was molded in brown. I bought at least one more a few years later; it probably was in the MPC box, and I remember quite distinctly that it was molded in olive drab. (I remember the faint sense of shock when I opened the box. I once bought an olive drab MPC Cutty Sark, too.)
I have a copy of the little book by Noel C.L. Hackney that Airfix published, shortly after the kit was released. (It was one of a short series, dealing with the "Airfix Classic" sailing ships and the 1/24 aircraft. Each book explained how to make additions and improvements to the basic kit. I remember ship volumes on the Victory, Mayflower, and Cutty Sark, and aircraft volumes on the Spitfire, ME-108, P-51, and Stuka. There may have been a few more. The aircraft volumes were excellent; the ship books weren't on quite the same standard.) It's pretty clear from the photos in the book, and from a few of Mr. Hackney's references (something to the effect of "you'll need a bottle of black paint to touch up mistakes"), that the kit he was working on was molded in black. I suspect the original, British issue was black and the first American issue was brown. But that's a guess on my part.
Regarding the question of scale - my best suggestion is to get hold of either C.N. Longridge's Anatomy of Nelson's Ships, John McKay's Anatomy of the Ship: The 100-Gun Ship Victory, or Alan McGowen's H.M.S. Victory: Construction, Career, and Restoration. All of them contain full sets of dimensions. Bear in mind, though, that the best you'll be able to determine is an approximation of each kit's scale. Most of them are out of proportion in one way or another.
In determining a scale for each one, about all you can do is pick one, easily-measured dimension (the length of the upper deck, or the distance from the figurehead to the outside of the taffrail), measure it on each of the kits, and find the equivalent dimension on the relevant drawing. I'd suggest taking measurements off a reliable drawing, rather than trusting a table of dimensions. (The meaning of "length" and "beam," for instance, can vary. Even an apparently obvious one like "overall length" can be deceptive. Does it include the figurehead? The bowsprit? The stern lantern? And measurements of beam in tables usually don't include the exterior planking, which in this case of course is pretty thick.) If finding the books is a problem, let me know what specific dimensions you'd like and I'll measure them on the George Campbell plans (the biggest I have).
I'll be interested to read the numbers. My guess is that, with the probable exceptions of Calder and Heller, they won't come close to matching the scales stated by the manufacturers.