It may be a real Z28. Yes, the engine's been restamped and the transmission isn't original (it's dated 9 months before the car was built), but the axle is BV0627G, a 4.10 posi ratio, and dated correctly for a 07E car, And since the 4.10 was only available on the Z28 and SS, there's a good possibility it's legit. It would have to be inspected by someone like Jerry to verify this, but even if it's not a Z28, it started out as an L48.
Ed