
Hiya,
yup, as you've found, you need to knock the corners off the hubs to fit them inside the discs. Should still be enough "meat" around them to safely fit the wheel studs, but I've always welded the studs in from the back, just to be sure.
The raised centre of the hubs needs machining down slightly to fit the centre hole of the disc, (that's what centres the disc on the hub to make sure it spins evenly, rather than the wheel studs). Probably easier to do that, rather than opening the hole in the discs -the hubs are a softer steel. plus if you machine the discs, any future replacement ones will need to be machined too.
I've got one complete pair of spare calipers somewhere in the shed, but I'm holding onto them! Loony's Dad has a lathe in the workshop. He could probably machine some replacement pins. Couldn't whoever's gonna turn your hubs down do that for you?