1957 AC system

[mirrormatic]

are the 57 and 58 components the same?
would the AC in a 58 roadmaster be interchangeable?

[wbdeford]

1958 supplement says, "A larger compressor of welded construction is used, with the head welded to the body.  This eliminates the possibility of any service on the internal parts of the compressor in the field.  The clutch assembly, the coil and coil housing, and the oil seal may still be serviced as outlined in the 1957 Cadillac Shop Manual.  The new compressor is driven by one belt instead of two as used in 1957."

So, at least the compressors are different.