temp probe location.

It will be off. I ran into the same thing on my car I had both front holes used up one for the fan switch and one for the Auto meter temp. I put the factory one in the back and found it to be off about 20°.
When the motor was down I had my machine shop weld a pipe fitting in the pan and am now using the factory water temp gage as an oil temp.

Scott

you can try routing the probe and cable differently or maybe consider moving the temp gauge..... where did you mount it exactly ?
mine had plenty of slack mounted in the dash

my oem temp gauge takes forever to register an accurate temp. some drives it never does. this is with it in the back of the intake.

make the autometer reach the front. your measuring with the water temp on the bottom of the pillar right?

Alternate placement for a temp gauge sender: This will allow you to keep the stock gauge for looks. Use the heater feed that comes off the intake manifold. Cut the rubber hose that connects the manifold water feed to the heater and splice in a tee adapter for the temp gauge sender. Be sure to use the same water feed line as the ECT sensor. That way you will get the most accurate temp readings.

Tee adapter info:
Make a pilgrimage to your local hardware or home supply center and get some copper pipe and a tee that fits the temp gauge sender. Solder two pieces of copper pipe onto a copper pipe tee with threads in the tee part. Find the correct brass fitting to match the temp sender threads to the tee fitting.



Keep in mind that the capillary tube on mechanical temp gauges cannot be cut, shorted severely kinked or damaged in any way. It is one piece from the gauge to the temp bulb that goes in the engine coolant.

You main challenge will be getting the wiring or capillary tube through the firewall. Do not use the steering column exit path for any wiring or gauge plumbing. Make sure you seal any hole you drill in the firewall with high temp red silicone sealer.