Brake switch for a 57 with an Lt1

[57kansastruck]

I installed an LT1 with 4L60E in my 57 Chevy 3100 short bed. I started it last week and I'm buttoning up the loose ends before I paint it . The computer raises the idle slightly if the transmission is in gear. Or if the brake is pushed. The stand alone wiring includes a brake switch lead. It requires positive power to the computer, until the brake pedal is depressed. This let's the computer adjust the idle if the brake is applied. The instructions ask that you tie the lead to the brake switch, sending positive power to the computer until you push the brake pedal. This is opposite of the way the switch works. The instructions say that older vehicles may need a different brake switch to work. I'm using a new four wheel disc brake master cylinder, under the firewall with the shortened stem stock pedal. Anyone out there ever done this? Any idea what switch I could use? Thanks in advance. Jason