'69 DartTrunk Mount Battery Disconnect Switch

You may want to consider a "push-pull switch" from Flamming River. You can mount it under the car and just mount a holder for the lever. Have the lever coming out underneath the bumper. And a side note, the lever can be taken off fairly easy so it only has to be there when you go to the track. It will have to be labeled "push off" which Flamming River supplies with a switch.