Inside the smaller bore is pitting where an oring is supposed to seal.
The flattest most square place to hold the caliper is the spot where the outer brake pad fits. Used a 2 inch square bar with a couple tapped holes to hold the caliper to the bar and have a solid mount to use on the mill.
Shims to get it square and concentric for boring.
Sleeves made from a scrap stainless pump shaft
Sleeves have flange to hold them. Brake pressure is on the flange end.
pressure side of the sleeve. I used Loctite 620 and a press fit .0015"