The 38/38 will work, just whether it opens butterfly without hitting smaller bore. It may well do it. I myself prefer equal venturis/throttles to have equal bores in manifold myself. I/m sure a 38/38 worked out would be gangbusters. The 38 if like most manufacturers refers to the choke portion of the carb, or the venturi diameter itself, not the actual choke WE here in the states talk about.
Weber, Holley, Motorcraft, Rochester, Hitachi, etc. they are all the same to me, the internal design features are what set them apart. I have no trouble understanding what every little hole and passage does in pretty much every carb made. And if not, I can figure it out in maybe 60 seconds by tracing the circuit to see what it does.