according to my wagner master catalog, these "should" be the same from late '58 to '62. at the catalog printing, there was only a kit available, and it lists it at a 1 1/8" bore, but without a piston. this number was good for all the big chryslers and desotos of that era. this kit also fit power brake cars as well, [maybe the reason for not including a piston ?] but i think the difference would be in the retainer ring bore necessary to retain the manual brake pushrod, where as the power brake piston would not require this. you may be able to get a power brake master, then swap out your manual master cylinder piston ?
just a thought, as i have no experience with this master.