I did some google searching today and found there is at least one 1953 Chevy 3100 that has the Brake Booster/Master Cylinder outside the frame on the driver's side.
The owner posted many photos of the build on another forum. From the photos, the brake pedal remains in the stock location, the rolling bar it is attached to was extended through the frame to the outside, where a lever linkage was added to push the master cylinder piston. The set up is similar to the stock linkage that GM put in the truck, just on the other end of the rolling shaft, that has been extended through the frame. It appeared very well built.
I am going to see if I can find contact info for the owner and/or the shop that did the work, to get more details.
