When I researched this, a specialist broker told me the ABT has it's own ABI number so it is rated by insurers. I couldn't find an insurer that didn't class it as a modified car though. Insurance comparison sites all seem to rate the car at 300 bhp, dig a bit deeper and most of those insurers decline to quote when told the car has around 350 bhp. That and the value being over £30k thins out reasonable quotes.