The 4.44 5 speed is a good option for an old 98 WRX that you probably don't want to throw $5000+ at unless it's pretty special.

They're a hell of a lot more durable than the 3.9 box the 98 came with, you'll struggle to find a 3.9 direct replacement as they're all rooted or half rooted already.

Budget on around $2200-$2500 for a decent 4.44 5 speed, matching rear diff and good oils installed.