Jack up the truck and tighten all of the shoes until you can barely move the wheels by hand. Huck brakes need both shoes per wheel tightened up.
Bleed the brakes in the normal, conventional way with a helper.
You are likely running out of piston stroke in the master cylinder before enough pressure is achieved to purge the wheel cylinders.
This is a very common problem.
Once you have a firm pedal, back off the shoes as per The Book.


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission