I picked up an old Chenowth rail last year and I'm finally ready to get started on it. It needs a new pedal assembly since the Brake pedal/master cylinder is seized up. I'm not sure if I need a 5/8" or a 3/4" bore when I order an assembly. The rail has twin piston disc brakes on the back (assuming they are serviceable) and no brakes on the front. I assume the bigger bore (3/4" and 7/8") is for larger caliper and 4 wheel brake systems, but I've never had to put much thought into ordering one so I want to verify. Thanks!