I don't care about mythical engines. I look at what I race against and what I see on racetracks here on the west coast and there aren't any fast RB, SR, 2J, or V8 Zs. There's one fast Skyline but it keeps blowing up. Amir's SR 260Z may be the first fast engine swapped Z I'll see on the track around here.
I'd bet those RB,SR etc powered Z's your refering to, that are nothing compared to yours, most likely don't have the money/ know-how/ driver that your Z does