Upgrading from kelsey hayes to???

This is the best I could find for caliper rebuilding. Go stainless steel pistons for sure. I remember seeing someone who professionally rebuilt calipers and used brass sleeves. Maybe it is not necessary with cast iron and stainless steel pistons. Mine were done decades ago with stainless sleeves and stainless pistons. Original Kelsey Hays disc master cylinders were 1.000 bore for manual and power.

Brake Sleeving & Rebuilding Services – White Post Restorations

Calipers Online