Factory or Owner Power Brakes - 62 c20

[83burban]

I am doing a frame up on a 62 c20. When i bought the truck a couple months ago, it had the special combination clutch and brake master cylinder on it. The clutch was blocked off with a fitting, and the Brake Master Cylinder went to what I believe is a brake booster, looks similar to the one in the picture. The line then exits and follows the stock route for the rest of the truck. Was there a factory power brake option for these trucks, or did some one pull one off a car and put it in the truck themselves. I have never seen one of these before on anything, and only found 2 pictures on the net - fit 1950's Cadillacs and Oldsmobiles.

I don't have a picture of the actual unit - it is being rebuilt. What is something like this worth, I don't plan on selling it unless it wont work for me. That leads me to my next question.

I am running 4 wheel disc brakes - Is there a proportioning valve built in. If not then i will run an adjustable proportioning valve for the rears.

Thanks - Kurt