So, I have a 98 Kouki front clip and
both pins of the oil pressure sending unit are used. The Z32 has the same sending unit and only uses one pin because there is an actual oil pressure gauge in the 300ZX gauge cluster.
Here's the wire colors on my 98 SR20DET
Yellow/Blue Stripe = Stock dummy light switch for gauge cluster
Yellow/Red Stripe = "Variable Ground" for the oil pressure Gauge
In other words, the sending unit grounds through the engine and there is no reason to ground one of the pins.
I've attached a pic of the sending unit and what the pins are for.
Now if someone could post pics, or instructions on what to trim to flip the gauge cover, that would be great.