Brake pedal is really stiff

I've always wondered if it was the prop valve as well. Wouldn't that affect bleeding though?

Probably not a bunch, BUT if you bled the brakes and was pushing the pedal tight to the floor you may have off centered the valve. If I remember correctly you can loosen one of the lines at the proportioning block and have someone push the pedal until you hear a click and tighten the line. You just re-centered the valve.

When you bleed your brakes put something like a 1 inch piece of wood under the pedal so you don't completely bottom out the pedal.