The way these work is when the ignition is on, power is going to the gauge.Ignition off, and no power to the gauge. The gauge works on varying resistance to earth. As the oil pressure rises, the resistance decreases in the sender, and the gauge rises. If you were to attach the gauge sender wire directly to earth, the gauge would rise to max. [this is what happened when you connected the sender wire to the wrong connector on the sender]
hope this helps.
What I mean with the spade connector, is if the original is too small to push over the brass lug, cut it off and find a larger standard size female spade and crimp it on the sender wire. AFAIK there are only 2 common spade sizes. Standard and half size.
My local shop that has done so much work on this 62...just didn't know about this, and I suppose the new sender had no installation warning. They are extremely conscientious, though. They will take care of it for me...and get the correct spade on with the info you guys have provided. I dug up a used gauge/receiver at Cruiser Parts. Much thanks to all.
One more thing. The extra lug on the sender is for making a proper earth to the sender body. It's not usually needed unless you use too much thread tape when screwing the sender in. The thread tape can insulate the sender body from earth , but this rarely happens, so probably no need to bother with extra earth.
**if the sender thread is made of plastic, the extra earth is essential.
cheers, and good luck.