Modloader priority

[Polaris77]

So in using the updated SCM mod among other things, I notice there is both an older version and an updated version. However, the newest version is missing things from the previous version (and I see nothing in the changelog making reference to that). So would I install both of them in modloader, only one, or what? Do I overwrite files, would modloader be able to use both files simultaneously? 

 

This is different modding than I'm used to so any help would be greatly appreciated