6" Lift anyone use Bilstein 5100 shocks

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Hey guys,
So I have a 78 K20 with a 6 inch lift. Pretty sure the leaf springs are on their last leg and I don't like the blocks in the rear so I am going to get new springs all around.
For now I want to start by replacing the shocks as thats what i can afford right now. Im thinking 5100 all around but I have been looking around the board and have seen mention of 5125 on the rear.

Can anyone set me straight when it comes to which shocks to buy?

Thanks