For the most part, they are all the same. There are some minor differences in the manifold connection (search for 'stepped port'), but these differences have nothing to do with Mercedes, and more with the manufacturing date of the compressor housing. Generally speaking, we are looking for early R4's with non-stepped ports, but stepped ports can be made to work with some fancy seal rings.

Advance is currenly charging $138 for a reman. Price has gone up.

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Bob
'82 300D Petrol B-G Metallic