Crane, hands down. They make all the cams for GM, and they work good, and are dead on correct.
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Go to the parts department at your local GM dealer and order it, though, as it will be cheaper and easier. Last time I checked the dealer's cost was right at $133, so don't let 'em rape you...
That thing is ground 6 degrees advanced, as it was from the factory, so you *might* want to look into retarding it, depending of course on the rest of the engine specs...