some of the vespa heads leak at the decomp when you put them on a 43mm cylinder. Not a risk that i would take, I always use an aftermarket head on them, vespas are hard enough to keep from leaking as it is.
with a proma and 13 carb, mine is running a 68 jet, gets moving pretty good too. definitely not the fastest vespa kit out there but its a nice boost over stock. I'm at about 45 but thats 13 carb, drilled intake, cut crank, proma pipe and mopedfactory variator