Help wanted!

Since brake fluid is a good paint remover, I wouldn't bother refinishing them. It'll just come off again. They came bare from the factory for that reason. All those early 60's cylinders seem to physically swap around. The difference I've seen is in the piston diameter. The smaller the diameter, the easier it is to apply the brakes but the more the pedal travels. Put whichever one you want on the car and see what the pedal feel is like. I would keep a retainer over the piston at all times unless you're going to pull it apart and rebuild it. I wouldn't blast anywhere around the piston as you my drive particles past the seal. Both manual and power brake cylinders have a piston retainer and they should swap. One is a finger type and other holds a dust boot, spring, and washer. You'll have to pull the push rod out of the manual one to use it in the power application. If you're going the other way, make sure you have a good grommet/o-ring on the push rod when you install it in the end of the piston. On a used master cylinder, I would just push the pedal down no more than 1/4 of the way when you bleed it, or, better yet, gravity bleed or vacuum bleed the thing so you don't accidentally damage the piston seal inside. Sometimes the cylinder will get a little corrosion farther down in the bore where the seal wasn't rubbing.