A mechanical switch is definitely the way to go...it'll be something of a nuisance to install, but it'll be a one-time nuisance, not the repetitive nuisance of a hydraulic switch. Also, the mechanical switch gives better safety performance, since the brake lights come on as soon as you touch the brake pedal, rather than once you've pressed it hard enough to pressurise the hydraulic system. The easiest switch to adapt will be a NAPA Echlin SL-169 or Standard/BlueStreak SLS-66. This switch has a long threaded shank for easy adjustability and adaptability to just about anything. You may be able to use/modify a '62-'66 brake light switch bracket.
Again, as always, your insight into parts #'s/brands is appreciated.