On the baby GMs the MU connection seemed to be a simple affair with a single cable between locomotives (all by the same manufacturer of course). I saw the MU working you referred to with the Black & yellow B233 in multiple with a 181. It had not occurred to me that such MUs occurred, over 2000hp with the more powerful 201 in charge. There must be at least 4 hoses on the 201s bufferbeams, possibly one for GMs, AECs etc, (hence my confusion regarding their purpose)?
When re-engined they would have been almost as strong an an A class had been, and much better equipped for heavy freight then when originally put into traffic