The correct booster would be a Midland Ross unit. That is the one with the lock ring around the outside. If your salvage yard has one, grab the mounting plate and the pedal while you are at it. You can use the '67 master cylinder which will bolt on the '66 mount plate. You will also need to source the '67 distribution block and fabricate the brake lines from the master cylinder to the distribution block. You would also want to have the salvage yard booster rebuilt.Thanks, would you think aftermarket or salvage yard source.