If I remember correctly there is a low pressure and a regular pressure switch that look identical. Seems like there were some peoples brake lights staying on with the low-pressure switch. I'm guessing the residual pressure valve in the master cylinder that holds a little pressure in the system when the car is not in use was just enough pressure to activate the lights. So, if your given a choice of pressures I'd go with the higher pressure of the two sensors. My sister has a '64 1/2 Mustang that still uses a switch that looks just like these, it screws into the master cylinder and works off of hydraulic pressure. In 1965 they changed it to one that mounts on the brake pedal under the dash so I'm guessing '64 was the last year for the hydraulic operated brake light switch.
I've heard of people using the Harley brake light switches, but I've never tried one.