Thanks guys. John, I have one RCDR from a recent Legacy 0-8-0. It looks like they made many versions of RCDR. This is what I have. I plan to make connectors for it next week and see what serial data looks like.
If anyone wonders why Lionel doesn't offer Legacy upgrade kits here is one reason. There are scores of versions of all the new boards. Gone are the days of an R2LC and DCDR. One size fits all.
Pete