After the initial big bore was created by mr merani's company, he contacted Guareschi. Guareschi thought it would be nice to race with that, and changed almost all. So he got the engine that was used in daytona to blast away the other bikes. The engine was raced in the italian supertwin series. There was another mgs01 active. The one from millepercento. They did see the potential of the bigbore too, and made a deal with mr merani to be the distributors for the kit. And last Eicma they presented a griso with that kit, to buy for only 29000 euros.....
What sort of bigbore you get from them, I don't know, not the one Guareschi races with, but thats to extreme for road use.
But try millepercento with a mail to ask for a kit.
When I was at the Guareschi shop last summer, they told me that then it was to premature to make a kit available. Next year they told me. Well it's next year, so maybe they can sell you a kit too.