Getting back to your origional question Mik, the reverse is a 'normally closed' switch, as you only want power through the switch when the reverse gear is selected. The top gear switched is 'normally open', opposite to normal switches because it activates the vacum solonoid that cuts vacum advance to the distributor. It wants to be powered all the time so that you get your vac adv except for when you select top gear. It is because it is a 'fail safe' system that ensures that if the switch fails and power is cut, you lose the vac advance all the time, thus ensuring that the pollution requirements are met. Stupid but a nessicary requirement at the time. If you are looking for a shallower switch, they should be the same thread pitch across the nissan range. Perhaps a later model box has a smaller switch.