2x3 legs go into a socket on a large pcb below The playfield.

The original switches do work, but a high speed ball is not registered every time. Only 50% registers and those are the slower shots. And two switches need to register, otherwise the shot doesn’t count.
Heighway went bankrupt. Schematics or tech charts don’t exist unfortunately.

My idea would be to attach the new sensors to the outer metal curved ball guide. After attaching them I would seal them with a thin layer of superstrong tape or epoxy. Or make the inner loop a dead end shot with the 2 sensors at the end. More than 1 solution to this problem.
But I understand it must all be wired and connected properly first.

Any chance a filter cap could help like on old Bally games? No idea but just a thought since that was something they did for fast shots.