Regarding the smallblock - instead of getting part numbers, just go to the junkyard and pick up several sytles of brackets. It will certainly be cheaper than new, and you will eventually get what you need. The best plan would be to find a complete motor with the bracket setup/style that you want, and cannabalize the entire setup, because it all matches. You can also buy an entire car, take what you need and sell the rest to a junkyard.
As far as the master cylinder goes, this type of side by side master cylinder/clutch master cylinder also was used in that era of Dodge pickups, so it probably is stock. Since the parts for those things were fairly standard, to could probably get a rebuild kit for a 60-61 chevy/GMC (thats where/when they were used on those truck) and rebuild your setup. You can also go to a brake specialty place and they could probably scrounge up a rebuild kit for you. Don't forget Napa, they still have parts for trucks that old. As a last resort, you can plumb in a new master cylinder for bothe the clutch and the brakes, just go to any junkyard that has recent cars, they have a lot of hydraulic clutch and brake setups that you can probably fabricate into working on your vehicle.
