no, not a safe assumption, nor is guessing about "the nature of the beast" .... I'm suprised you took a new-to-you truck in unknown condition on the road without first checking over the brakes - if your brakes don't start to apply until half way down they need adjusting &/or fluid and maybe new shoes
that bumper isn't inches thick, more like an inch or less, it's intended to prevent the metal pedal arm from banging the bottom of the floor, not to set the height of the pedal, which from the factory sits as much as an inch higher than the clutch anyway
Bill