The Killer B M20 to 1/8" NPT or PT Adapter will allow the use of aftermarket oil temperature sensors that have 1/8 NPT or PT threads. The M20 thread is the same thread pitch as the stock oil pan. This adapter is compatible with both the Killer B aftermarket oil pan, and the stock Subaru paN.
Measure the oil temperature where it should be, in the pan!
Select your gauge sender thread style -- NPT or PT (also known as BPT/BSPT).