I'd talk to Quaife, but I think a far better route is to buy a clutch from AP racing with the correct centre in it. That's going to be a much cheaper and almost certainly better solution.
As Steve suggests it would be far easier to find a clutch plate that fits within the KV6 flywheel and pressure plate. There's quite a bit of choice in both Ford and other manufacturers parts. What diameter friction plate do you need?