To make the converter clutch work "as designed" you'll need the factory vacuum switch, and a brake light switch with a "normally closed" set of contacts. The switches are wired in series, so either touching the brake or having a low vacuum condition (acceleration) disengages the clutch. The third switch in the daisy chain is inside the transmission, and only allows the clutch to engage at a governor pressure equivalent to cruise speed (45+ MPH) depending on the rear axle ratio. This provides several stages of "idiot proof" to prevent the clutch from staying engaged at a stop, or during low-speed operation.
A simple toggle switch would also work, but you'll embarrass yourself by leaving it on at the wrong time occasionally.
Jerry
