Rear steer, both active and passive, was a bit of a fad in the 90's, especially with the Japanese. Most racers who use those cars now actually buy kits that defeat them, as they are unpredictable and unreliable in nearly every incarnation that has been tried yet. The only one I know of that was really good and still used in the racers is the Porsche 928's "Weissach Axle."
Don't waste another minute waiting on parts, or anything else. Just get out there and start racing! You will suck at first, and you will be slower than many other cars, but the only thing you will regret is not starting earlier...