I should be clear and say that I don't build custom big brake kits anymore. So I'm not trying to drum up any business, I'm just saying that it is fairly easy to build a custom kit once you have the correct frame of reference. Since the hubs are custom it doesn't matter that an Imperial is different than a C-body. All that matters is what the bearing bore diameters are and what the spacing between them is. Then you need to know the bolt pattern, the diameter for the rotor center, the centerline for the rotor and the hub seal diamter. Once you know those dimesions the hub designs itself on the CAD system.

Like I said before, I don't build these anymore but guys like Kore3 build custom hubs. Baer builds custom hubs if you know who to talk to. DoctorDiff can build custom stuff, etc. If you have the money you can get the job done. You should really pick the wheels first though since the wheel design will drive the brake design. Ideally you'll want a 17 inch rim with plenty of caliper clearance.