First, there is a TS12 forum and TRS2006 forum, so those folks would know best. For TRS2004 to TS12, I use the contentdispatcher.exe. Not sure if this was incorporated into '06 Content manager or if it was still a separate program like in '04. Basically you export the loco and its dependencies to a .cdp file, then import that file into the TS12 content manager. The standards between the two are notable, so you may get some warnings or errors. In general, Trainz has gotten less and less tolerant to deviations from "correct" asset creation as time goes on. What was acceptable in '06 may not fly in '12. You have to deal with whatever pans out. If you are lucky, the assets have been updated to TS12 level (build version 3.5 to 3.7), look at all versions of each asset in the TS12 content manager for updates. Do not download anything above version 3.7, it is for later Trainz releases.