Considering how long they have been making compressors, it's quite unlikely that they are internally the same. Similar, sure. They all pump refrigerant. One big difference is that older compressors are fixed displacement, whereas many newer compressors are variable displacement.

Swapping from a E to a D of similar years should be just fine if the mounts are the same. You could look for the presence of the bellows in the low side (back end of the case) to indicate variable displacement. It will be about 1" in diameter, just below flush with the outside of the case, and held in with a circlip.