What have I got here?

I'm betting you have a Master Power Brake conversion package there - link.

Caliper bracket has the letters "MPB" cast into it, which is partly why I am guessing Master Power Brake.

Can't tell from the picture, but I would bet the spindles are reproductions, the caliper brackets certainly are. Rotors are 10.87" based on the fact that the dust shields are slightly bigger.

Might be SSBC, seems like everyone was doing a kit based on reproduction spindles for awhile, but I didn't find anything on their site to verify that they used to sell a similar kit.

There was a recall on some reproduction spindles, might want to look into that, too.