This kit includes everything you need to mount your AutoMeter oil pressure sender (or any other 1.5" or 2" diameter electrical sender with an 1/8" NPT fitting) in your WRX. It includes a custom adapter that threads into the block, a braided stainless hose rated at 3000 PSI, stainless mounting brackets, and complete instructions. All you need to do is wire the sender to the gauge and you'll be done. Mounting clamps available for 1.5" and 2" sender body diameters; specify below (for AutoMeter, use 1.5"). Gauge and sender not included.
The block adapter is also available by itself here for smaller senders from manufacturers like Defi that do not require relocation for clearance reasons, or if this location is being used for an oil temperature sender installation. It is threaded for an 1/8" NPT sender.
Download installation instructions here.