Get in touch with one of the tuners on here (Abbey, H-dev, TDI etc) and ask them. Probably your best bet would be to find a proper SC kit from GTM, Vortech etc and get a discount for not including the SC, that's assuming the mounts for the SC you have match (GTM use Rotrex iirc but even then you'd want to check). To put costs in to perspective for a later HR engine you'd be looking at £2.5k for a new Rotrex SC unit but for a full SC build you're talking £10k+. Even if you can get the SC for £100 you'd still need the other £7.5k+ unless you're doing all the work yourself (considering the above I'm guessing that won't be the case).