Modern Vespa

Ive got the diagrams via beed speed

One bit of clarity needed

Do all three wires (horn .lights,brake) form the VBC loom ALL get connected to one single connection coming out from the 12v regulator.

ie do all three things..horn..lights..brake lights all get their power together from the one single 12v out put terminal on the voltage regulator

If so, I will mount all three to one terminal on the original junction box and then run a wire from the volt reg.

or am I way off?

That's how I did my VBB. just bonded all the wiring together on the 12V regulated out of the regulator.

You'll also need to swap the brake pedal switch to a normally-open, because it will now need to connect to activate the brake light rather than be shorting to ground to kill the light as in a balanced AC system.

Thats how I did mine as well.