Depending on what condition the engine's in, and how it's built.
If the bottom end's balanced, with forged rods and lightweight pistons, a mild to 3/4 cam, and adequate intake and exhaust, then you should have absolutely no problems pulling 5500-6500 rpm. And no problems holding 3000-4000 rpms for extended periods of time.
On the other hand if none of the above applies to the engine, and there's significant wear on the bearings, rings, etc., and intake and exhaust are stock, then you'd do very good to pull out 5000 rpms.
Maybe others can add more insight.
-ftyler
