I am working on doing this now on my truck. I am replacing the cheesy dealer AC with new OEM type components. As Russ mentions, you will need the engine side AC plenum in addition tot he other usual parts like condenser, hoses, accumulator, evaporator, orifice tube, orings, etc. The wiring harness, at least on the used AC plenum I bought, was already installed. Here are a few pics of the engine side AC plenum I purchased from a '95 truck. Yours may be slightly different being an '88. I am going to take more pics as I install the AC, but it is going to take a while as I am replacing head gaskets as well.
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