The easiest way would be to open the hood, look at the engine. In particular, pay attention to the valve covers. If the valve covers are smooth and their are four small diameter tubes going through the center, then you have the LB7. On the other hand, if the valve covers look "sculpted" and you see the end of the injectors protruding though, then you have the LLY.
Look at the following pictures of the LLY and compare your valve covers to it.
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