68 C40 pizza truck Brake issues

[Unofornaio]

Thanks Bob after no replies I cut all the info off my original post to get to the point quicker.
What I've done is go through the entire brake system. Replaced all the wheel cylinders inspected and measured the drums and shoes all we're with in .038 of new. Flushed lines put everything back together, adjusted and bled. Another member stated that I skipped a step which was pressing the pedal to center the shoes and I should still hear a slight intermittent sound after that and not back off like I did. While I I believe this is the correct procedure despite this I am now convinced it is the booster.
But once again finding the part is going to be a journey. I'm fairly certain I found them at Napa but will not know for sure which stroke I have on it until I pull it.
Thank you for taking the time to reply I do appreciate it.