that's a pressure style brake switch. the stock brake switch is electric and activated off the brake pedal arm. there should be a bracket on the swing pedal frame assembly that the switch snaps into.
if you're lucky, the stuff is all still there and all you need to do is connect wires. or maybe sort out a little wiring.
another option, which i totally hate is throwing a T in the line with an adapter and running a pressure switch there.