Look at it this way. Huck brakes had been in service on millions of vehicles and they worked well.
Bendix brakes were an improvement but not a necessity for previous years.
I6 engines were eventually replaced by the V8 but I6 engines still work well today.

If you plan to do frequent expressway driving at 70+ MPH then I would invest some $$$ and convert the front to disc brakes, ditch the Huck and Bendix.
If you plan to cruise around town, back roads or do farm work, the original brakes are just fine. Keep that $$$ in the billfold.

I converted my 50 3100 to Bendix because my spindles were bad and good 52 parts were available.
It economically made better sense.

The rear axle I would want is the one that is in good condition (gears, bearings etc.).
Rear axle gears and bearings can run into a ton of money.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."