Jake, try posting this on the TMCC/Legacy forum.
Guns or GGG are your go to guys.
I found this tricky as I installed a Cruise M on a Lionel Dreyfuss Hudson. As you say the instructions are not clear when it comes to steam installations. If I remember correctly the examples are diesels and a Kline steamer.
Check this topic and see if it helps
https://ogrforum.ogaugerr.com/...4-cruise-commander-m
Nick