Pirate jack disc brake kit.

Could be their using all 73-up spindles, calipers, caliper mounts, etc, and maybe they are having disks/hubs made the same size as large bolt pattern stuff, but with the small pattern.
I don't know anything about these guys, never heard of them. I'd certainly want to talk to them about this on the phone before ordering anything.
x2 on that. It would be pretty neat if that is what they're doing. Different, for sure