Pedals are in. Managed to get the entire assembly moved forward by 2 inches, compared to where the previous setup was. Had to hack up the pedal arms a bit, and the floor won't be able to be nice and flat at the firewall (the pedals would hit the floor, so I'll have to sink it down a bit), but it's reasonably comfortable. There's no getting away from this truck being cramped without stretching the body or having the pedals protrude through the firewall, so I think I have it about as good as it can be for pedal placement. The seat being lower and slightly farther back also helps.
Will need to cut a bit of the firewall support structure to allow better room for my foot when the clutch pedal is fully depressed. But I get full pedal stroke out of both pedals. Not sure why, but this feels like a huge item to check off my list. (aside from plumbing the lines and making the pedal feet, and shortening the brake pedal plunger rod just a little bit for a slight bit of play). I've been playing with the pedal placement off and on for a while now, this is revision #3 of the pedal arms themself. I started out not wanting to have to cut them, should have just done that from the get go. Feels good to have them in place now, and I'm happy with the placement. :)
Told myself, don't think about the floor design, just get the pedals feeling good, and worry about the floor later. And yes, both reservoirs for the master cylinders will be below the floor, won't have to make the access panel raised up or anything, it will be flush with the floor. And the floor will already be about 2" lower than it was before. Clutch reservoir isn't on there at the moment, just have a plug plugging the hole.
Doesn't look as cramped as it really is in the photo, but everything just barely fits when the pedals are fully depressed.
Bolts at the top of the pedal arms are there just to keep grinding dust from getting into the threads. I'll have to make some pedal feet, I haven't decided what exactly I'll do for them just yet, but will probably spend entirely too much time making them either way