I finished the build on the footwell extension finally. There is no "elegant" solution to get 3-5" more legroom on these old trucks (After all the other mods we've done like the seats etc)...but we're the only ones I know that have ever gone this far to do it.
I used a stock floorpan patch panel, flipped and hammered slightly to make an extended foot egress. Then we made panels to box the toe area, and angle the corner to keep a better shape around the engine. We also trimmed fillers to allow us to retain two factory grommet locations, where the ECU harness is and a few other things passing through. I primed and bedlined both sides thoroughly, then modified some stock carpet to fit comfortably.
It adds anywhere from 3-5" of foot room depending which part your measuring. The toe box that protrudes into the engine bay remains well-tucked under the steering column and shaft, and doesn't interfere with any header clearances. At full lock on 235/70's, I have well over an inch of tire clearance at full compression, and around 2.5" under normal conditions.
Its not a "sexy" mod like the performance stuff, but it allows for way more comfort, and more ergonomic food positions. The dead pedal is great for the left foot, and but the new toe box is wide enough for two size-14 feet in big shoes if needed. Its sooo nice to be able to stretch out my legs.
The brake and gas pedals are actually out now. I'm building a new pedal stalk (goodbye shotgun barrel pedal, I'll miss you!)...out of the DBW pedal base, and the DBW pedal/pivot piece, and some steel. The brake pedal pivot is out as well, and I'm fabbing a new pedal assembly. Its retaining that stock pivot point, and stock pedal rod location so the structure will be essentially the same. The main difference is that the pedal itself will exit in the clutch pedal location, gaining the 2-3" lateral movement we need to center it in the footwell.