Welcome to the board. I've been using my 52 for a daily driver, will try to help y'all out.

Master cylinder - If you want to stick with a stock one, your local mom & pop parts store should be able to get you one. If they can't, they are available throught the vendors found in the links section at the top of the page.

Bracket - I assume you're talking the lower bracket and a 235 engine. I was able to extend the slots on my original and make it align. Hopefully someone else knows of where you can buy one.

Disc brakes - No conversion kits for the 3/4 ton. I keep hoping someone will make one.

Tires -- If the same as my 52 originals were 7.00-15 6 ply.

Rear fenders are available from most any of the vendors.

The two major drawbacks to the 3/4 ton are wheels and gearing. Not a good solution for either. The modern wheels set about 2" too deep to use on the front axle. This is more than can be spaced out without custom made spacers to the tune of about $100 each. I have been told of companies that change redo the wheels, but haven't tried that route. It's not cheap, either. I'm running the original size tube tires on the front of mine.

Rear tires I went to modern 16" wheels and 7.50R16 tires. There is about 1" clearance between the tire and the frame. I transferred the hubcap clips to the newer rims so I can run my original hubcaps.

Gearing for the std 3/4 ton is 4.57, which limits your highway speed to about 50. I bought a differential from a 64-72 with 4.10 gears and took the pumpkin (center section) and made a swap. This, along with the taller tires, made an 18% improvement in highway speed.

Fred
52 3600
69 C-10