no, just go straight to a specialist insurer
adrian flux insure my turbo'd cabrio reasonably priced too, all mods declared
when I was looking for a car I first spotted a turbo converted escort bonus, website gave me a quote but cabrio I've got came back a lot dearer of the website search quote so I phoned them up and they sorted the quote to the same as the escort bonus turbo price, so I my advice is give them a ring, infact they will phone you