You mentioned testing vacuum going to the booster, but have you checked the new booster itself for proper operation and vacuum leaks?

Pedal assembly in good shape not binding at all?

Not trying to be a jerk just cant think of much else that you havnt replaced yet

Another question would be was the truck stopping properly before the brake replacement or was this the initial issue to begin with?

Is the parking brake working well?

Not sure what the grinding noise would be unless somthing isnt right inside the drums binding maybe, or was it a problem before the brake replacement or is it coming from somewhere else possibly drivetrain. But I wouldnt know with out hearing it myself just guessing

Sorry for all the re edits. Was re reading your initial post and had missed a few items youve checked/replaced. I hope you figure it out cause im pretty much out of ideas already myself