For easily-had stuff, my vote is for T6 5W-40, M1/Edge 5W-50. All of them have decently high ZDDP levels, Rotella T6 is seen as oil of the gods by the Subaru guys. Edge 5W-50 has more ZDDP than T6 as well as Castrol's fluid titanium for a bit more protection.
If you can get it locally, Red Line 5W-40 or 10W-40 would be my pick personally. I'd keep the OCIs short and sweet. Not sure about filters and if you need to use certain ones like K&N or Fram Racing ones to meet track or SCCA rules. My head says OEM Mitsu or Fram Ultras would be fine for the street unless a Hyundai-sized filter can work(and the newest Wix 51334s are made in Korea by Mann+Hummel Korea, like OEM Hyundai).
I'm not sure if the Mitsu 4G63 has a tendency to grenade like the Subaru EJ207/255/257. Regardless, rebuilds are a fact of life once you start playing with power.