In my Previous Post I describe how I used a Jeep Oil Pressure sender to create a calibrated oil pressure gauge.
This morning I worked with David (na300zx (OH)) complete the same mod on his car. We learned a few additional details worth sharing.We started with an Autozone sender for a 78 Jeep CJ7 which was a Wells PS151. This unit had a threaded stud for the sensor wire connection.
The PS 151 would not work for this mod. The initial resistance is too high instead of too low so it would
not be easy to calibrate. David made a run to Advance Auto and found that they offer two styles. One says it
is for Jeeps with a 3" gauge which looks to be the same
as the Wells PS151. The other is listed for a 1" gauge
and has a lug contact on the end. This is the one you want! PN S330P.
AND it is a whopping $12.99.
We proceeded to profile the sensor and found it had
initial resistance lower than a stock sender so it can
be calibrated easily. Here is a photo of the test setup with the Wells unit
on it. With this setup, connect a wire to the contact.
Crimp a male spade terminal to the other end then
cut the wire in half and solder a 20 Ohm pot in the
middle.
 Connect the spade terminal to the car's oil sensor wire
and attach a second wire from a good ground to the housing of the oil sender. Turn the key on then pressurize
the test rig and compare the test gauge to the in dash
gauge. I recommend setting the air pressure at 60 PSI.
Adjust the pot until the dash gauge matches the test gauge. Now use an ohmmeter to measure the resistance
of the pot. De-solder the pot and solder in a fixed resistor
of the same resistance (or very close) and cover it with
heat shrink. After completion we profiled the gauge at 30, 60 and 90 PSI. It was nearly dead on at 30 and 60PSI and was a
little more than 10% low at 90 PSI. It is now far more accurate than the factory specs call for and cost less than
$15 total rather than the $80 Nissan wants for a unit with
poor accuracy and may only last a few years. 
Now install the sending unit in place of the original and
ty-wrap the wires securely. We also put a dab of RTV on
the solder joint at the sender to seal it from the weather. 
Optional info:
A slightly more accurate setting is obtained by testing
with the engine running since the gauge is voltage
dependent and running the alternator boosts the system
voltage 1 to 1.5 volts. We chose not to do it since it just
made the whole area hot and difficult to work on and if the
sender is removed soon after the car is shut off, significant
oil leakage may occur.
It might be possible to make a cleaner install if a spade
terminal was soldered directly to the lug on the sender
and the resistor was spliced into the sensor lead on the
car. We chose not to alter the car's harness permanently
at this time. These are photos of the box my sender came in from
4WD.com.
 This is the box the $12.99 unit from Advance Auto Parts came in.
KKROFFTNow occurs everywhere, simultaneously. But it doesn't have to be experienced the moment it happens. Every now that ever was is still exactly when it was, when it was now.
Then, in terms of perception, is nothing more than all the nows that are no longer now. Thus, the difference between now and then is when. --The Waystoppers Users' Manual 
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Update to my Oil Sender replacement post - 
