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With what you have either you need to space the whole bracket assembly off the frame or modify the arm. The one thing about putting a Z in the upper part of the pedal is that it's going to shorten the arm how ever much you Z it. I would either box in that part of the frame or build a spacer of sorts out of thick wall square/rectangle tube.
Decided to return the plates to midfifty and make my own. Used 1.5" hole saw for brake pedal and 2" hole for column. Had to grind column hole a little larger for it to fit. I think it looks great. The column mount is a piece of exhaust tubing that will have a couple screws securing the column. Kinda like the 2nd pic here. First pic is mine.