Pirate jack disc brake kit.

I think they are close to 11, maybe 10.8" or something. But those calipers look like 73-up BBP style, and from the pics even the disks look like BBP to me.

Yeah I hadn't even noticed that. They definitely look it. Could it be possible they used those calipers because they're more common? Is it even possible to use those calipers and have SBP?