I just souped up a stock v1, went from about 28 to close to 35. Doesn't sound like much but makes it very rideable.
Sha 14 (15 would be better but this is a free used carb) with a 62 jet and opened up air filter. I've already got the bigger intake that's like 14 stock but check that you don't have one of the tiny ones.
Stock motron exhaust with the restrictive outlet cut off, didn't cut off the whole baffle just the last assembly with the 2 discs and tiny tube
Ported stock cylinder, 1.5mm up on the exhaust and about 2mm wider each side. Intake didn't go much lower but maybe 2mm wider each side, can't remember exactly. Removed stock head gasket.
From here the next best thing would be a cheap circuit pipe or slip on chamber. I built a really similar engine to this back in the day and had it up to 38 with just an ev racing pipe, even faster with a 15 Bing but I never gps'd it.
Stock v1 porting is crazy restricted, even on the 'fast' cylinders. It doesn't take much to get them over 35.
Obviously check bearings, chain, tires, breaks, all that stuff for drag too. The cheap stamped brake plate that a lot of Italian bikes have likes to hang up.