Harold,
I can only speak for myself, but part of the fun of building a Flathead Ford is knowing the limitations you have to start with. If you know 1953 was the last year they made Ford Flatheads and you build your own motor to the rules, you take the limitations of the motor into consideration, and build it accordingly.
Now once you have done all of this and spent an enormous amount of time and money, someone finds a stash of French Flathead blocks and or someone starts making aftermarket Flathead blocks and immediately wants them to be legal for the vintage class. What is so vintage about a French flathead block or an after market Ford Flathead block? Like I said to me part of the fun is building a better mouse trap with what you have, and knowing its limitiations, and also using a vintage block. But that is just the way I feel about it.
Tom G.