Sounds very similar to what I play on running!
Superbravo, Moparts aluminum racing subframe, stock cases, Kinetic CDI 9.49:1 CIF gear set, Polini variator, and also an MLM watercooled head. I've got a lot of wheels to pick from but I'm probably running some cool 10 star mags in the back and some 8 (I believe) star rare plastic polymer wheels in the front (we'll see if they fit). I like how skinny these wheels are. I have yet to find any radiator parts or a pump, etc.
I am going to instead be running the Malossi 43mm, probably stock rear pully and I have some springs I can play with. Mazzy anti special racing crank or potentially a drilled out stock crank with a 13mm hole in it (I haven't measured the crank yet to see if that will work, and I need to do some flow calculations and porting math but I think that's what I'm looking for.
The air inlet on the rotary side is opened up to 13mm like yours, and then like you said the pinasco half is 13mm, I may see about trying to open that up a little and potentially run a different intake that sits on a slightly different angle. I need to inspect the case half when I get it. If I don't modify it I'll run dual SHA carbs probably unless that's un-tuneable. I am unsure on pipe right now. Hopefully by the time this build comes to fruition Cranks can have his vespa pipe done, otherwise I will probably run a calibrata as well or I may modify a huge chamber onto a metrakit pipe I have.
Are you going to thermosiphon with your MLM head? I am opting to run a pump first so I don't have to worry as much about flow and cooling while tuning, but will probably try to upgrade to a siphon setup in the future.
Anyways, @andysimpon it's good to hear you've actually seen one in the wild a few times! I feel like dual carbs or not, vespas are often hard to build for serious speeds. That 50-60 range seems to be incredibly hard to achieve even with dual carbs or huge kits and aftermarket cases. Hopefully someone can chime in on the exact details of that build, would love to hear more.