Which hydro boost brake is in my truck-JH2, JH6, JH7? How can I tell? 04 sub2500

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I'm looking for a replacement power booster and I don't know which it is. When looking up parts it's states for use with a particular JH system. How do I find this? I have a 2004 Chevrolet suburban 2500 4x4 6.0l.