Brakes all replaced but master cylinder still having issues.

[Krex]

Brake problem this is a 1970 k20 lwb with drum all around.

Replaced all wheel cylinders, rubber hoses to cylinders, replaced all shoes,

Reused hardware where I could no leaks that I see in the system bleed brakes in correct order , feel pressure on brake pedal, but still spongy but before had nothing, truck truck on and put it into reverse and I can not stop truck put it in drive can not stop truck,

I think the last thing to replace is master cylinder but, it holds fluid and I see no leaks

What should I do next????
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