Cars, small boats, etc. are not affected, they are generated in a different manner.
The only way to keep your ships is to convert your FS2004 traffic files to FSX format.
There are 2 utilities available:
Flightplan BGL Converter-at the bottom of the page-simple '1-shot' converter. Extract the zip to a folder and run the .exe. No help file but simple to use.
AIFPC by Peter van der Veen-link in message #57- traffic file decompiler/compiler. Two step process to convert: 1-decompile FS2004 file; compile to FSX file. Also allows for the creation or editing of traffic files using the
TrafficTools v2.02 method's .txt source files. Extract .zip to a folder and run the .exe. Help file included.
Both utilities allow batch processing and file renaming to distinguish FS2004 and FSX files.
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.