If you have a more modern front suspension and rear end, those brakes are Bendix brakes rather than Huck and should be self adjusting. You’ve got a leak somewhere if you are adding fluid or a bad master cylinder, and or air in the lines if it is necessary to pump.
Depends on how modern the front brakes are. Self adjusting brakes were added by GM in 1963. I had a 72 K10 pickup that had self adjusting brakes.