John,
It is a LCRX, Lionel part # 610-8124-110. I'm not sure how that compares to an R2LC. Did some more searching in the supplements and found a overall wiring diagram using the LCRX that should be similar to my setup in the Milw dummy B unit 6-18139. The diagram is for a 601-8133-000 NP B unit and is in Supplement 38, S38:2-3 (C-63-3). Of course they don't give actual pinouts (ie pin # and what it's function is) for the LCRX but they show what the pins that are used go to in the B unit. I'll check it out when I get a chance and perhaps post a reply to my original post on this issue.
Ken