Thanks Aaron. I thought the '98 Forester was Phase 1 DOHC like the RS, but I'll say that we should probably all listen to the guy who works at the actual Subaru repair shop on that one.
Also, Redline Water Wetter is the second best way to help prevent the HG issues. ASSuming you get your coolant system bled properly, the WW will help to prevent bubbles from forming and causing the hot spots by changing the surface tension of the water/coolant mixture. There's a write-up of how and why it works
here. That author references Redline's White Paper
here. Just about all of us who read this will benefit by adding it to our cars.