NOT MINE 1966 polara 4 speed!

It took years to learn all this 4-speed stuff, and over the years my memory is starting to fade on it.
My memory is getting refreshed.

So seems that the clutch/brake pedals are the same "length" whether for MB or PB.
The PB bracketry is taller where the brake pedal attaches. But the bottom edges of the pedals are aligned when the pedals are loose from the car.
When in the car, the MB pedals are side-by-side, while the PB pedal will be closer to the floor.

And this makes sense, as a normal PB pedal has less travel and is closer to teh floor, a MB pedal sits closer to the seat.
And makes sense that the clutch pedal is in the same location for both, as the clutch linkage cares not what type of brakes the car has.