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The only place I have seen that switch is Ebay for $50-100. That switch is almost impossible to disassemble without trashing it. I converted mine because I was concerned about having brake lights that didn't work, brake lights are too important.
Unfortunately this conversion will require both 69-up PB switch brackets (I believe both are available from Zips). You will have to make a plate for the switch bracket because the 68 pedal assembly is not drilled for it. I wish I had pictures of what I did. You will also need the connector from your 68 switch (or one like it).
I just saw a thread where a guy made a bracket and mounted a later style switch. Worked like a charm and the cost was low. I can't seem to find that thread though.
The reason you had problems with the position of your pedal based on the new setup...is pretty easy in theory but hard to fix. I'm guessing your car used to be a manual brake car? The hole in the brake pedal where the clevis clips is in a different position on the pedal, giving you more power via a fulcrum effect.
The power brake setup has a different length rod, changing the dynamics. You can do what you did, or remove the pedal and drill a hole int eh same position that would be found on a power pedal.