clone engine?

[tirebird]

I posted the below message over at the Chevelle board asking their expert opinion about the authenticity of my engine. I'm curious about what you guys think.

John

Last year I purchased a 1971 Pontiac TransAm with an LS6 engine. The documentation was impressive, including several articles in popular hot rod and muscle car magazines showing the warranty replacement LS6(from Berger Chevrolet) going into my car. The author of the articles was the second owner of this car who wrote in great detail why he chose the "grand rodent" as a power plant over the then(1972) trashed 455 HO.

When inspecting the car I duly noted the stamping on the front of the block, by the alternator, "TO417CRR". That, along with the articles, and the reasonable price, was enough for me.

Today, while adjusting the valves for the first time, I decided to note the other important numbers: block casting number:3999289, Heads; GM5T, HiPerf., A1472, casting#3964291.

Do I have the real deal or merely a poor imitation? Let me add that I'm happy with the car because, whatever is officially under the hood, is enough to chirp the tires during the 2-3 shift at 70 with a TH400. But, I'd like do know the truth of what's really powering the beast.

Thanks for your help.