Hohner H is definitely very different from Hohner Artiste, which in turn is different from Hohner Germany.
I expect that T, H, Artiste scales will have their own consistent sizes over the decades (otherwise what's the point in having a scale), but I don't care much for T and H. Artistes are the business, Hohner Germany are sweet & good quality, the rest can go into the bin as far as I'm concerned.
Italian reeds can be different between different manufacturers, but from memory, their higher end tends to be significantly longer than same note for Soviet reeds, and bass end is shorter than equivalent soviets.
You also sometimes get narrow-plate reeds, but I doubt you'd see them in a 48-bass.
Problem is, even if you're out by a mm or two, that's potentially a lot of time wasted chiselling reedblocks. And low end weltmeister reeds are not anything to write home about - if you're going into the trouble of replacing reeds, get something good. Unless they are (almost) free and you have time to waste hot-rodding them by rolling & chiselling.
I don't think I'd 3d-print reedblocks... PLA can warp quite easily and is quite heavy. ABS is also dimensionally unstable I believe.
I laser cut mine from layers of 4mm and 6mm ply, then glue them together.