If there is LOTS of air in the system, the pedal will indeed stay on the floor. I believe you have air in the system. Since the system had really nasty fluid, I would recommend rebuilding both cylinders, reassemble and bleed. There is no need to replace the whole cylinder unless they are pitted.

Remove both cylinders and disassemble. LIGHTLY hone them, then clean and inspect. If there are pits present in either or both cylinders then replace any pitted cylinders. For a cylinder with no pits, go to a foreign auto parts store and get rebuild kits. These cylinders rebuild easily and rebuild well.

Since DOT4 fluid is much easier to find than it used to be, you might want to use it, but I've never used anything but name brand DOT3 in my 123 cars with no ill effects at all.

Good luck,