If you're running a GM HEI distributor, grounding the "tach" terminal in the cap beside the power input wire will short out the ignition. If you're not running an HEI, you're about to have more problems than an overdrive can solve! A micro-switch with "normally open" and "normally closed" contracts mounted under the gas pedal will replace the kickdown switch.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!