[mitchntx]

Glenn has done tons of research on this and we are both about to the point of have custom machining done.

Autometer guages have a sending unit that is 1/8" NPT.
An LS1 motor has ports machined in, but are 12x1.5 metric.

Sure there are adaptors, but the wall is so thin the adaptors twist off with MINIMAL torque. And by that, not enough to crush a seal enough to prevent a leak.

Why don't they make a 12x1.5 sender?????

The stock sender ohms out WAY different ... almost 1K ohms lower than the AM.

[ampcory]

You can contact Auto Meters service tech support department for a 12x1.5 adapter that does not break. if using an Auto Meter short sweep electric temp gauge, they will sell you a adapter and sender for $18.49 and free shipping to the US. If using a Auto Meter Cobalt or C2 full sweep, the adapter only is needed with no new sender for $12.00. I have installed several with great results. The replacement sender does not have an extended probe so the adapter can maintain a thicker wall thickness. It is also not in the way of headers.