Lionel has been selling their Legacy boards for a few years now. Actually started selling their first generation boards nearly ten years ago
Well that is very interesting to say the least. When I first came into the hobby a few years ago, I fell in love with Legacy and immediately started exploring how I could customize non-Legacy S scale locos to add this functionality. I was told consistently by several experts that you could install ERR's TMCC boards, but that Legacy boards were not available for custom installations. I then did many TMCC installations in non-Lionel locos. Over time, I tired of the limits of TMCC and the small selection of railsounds boards and switched to doing DCC customizations. In that time, I have never read or heard mention of anyone selling Legacy boards or of anyone doing a Legacy custom install. In fact to the contrary, I saw the market go crazy when ERR closed its doors and we almost lost the ability to buy TMCC boards. I can't imagine why people would have cared about losing access to TMCC boards for custom installs if Legacy boards are readily available for such.
I would love to know more. After reading your post I ran several searches on OGR, on Lionel support/replacement parts page as well as broad Google searches, but found nothing. Can you give me any other leads such as the name of a dealer who sells them or the name of anyone who has custom installed a Legacy board?