Rebuilding or Swapping Internals on a Power Brake Master Cylinder

The original looking master cylinders with the round front lids are very hard to find and cost a chunk of change when you do find them.
Does anyone have some experience they can share on rebuilding a factory master cylinder (MC)? Even the kits to rebuild are expensive. The rebuild kit I need is $145.

I am also curious on whether it is possible to swap internals from a new and far less expensive master cylinder into a factory MC with the same bore size.

3461187 Master Cylinder (2).JPG 3461187 Master Cylinder (6).JPG
Author: MoparCarGuy